My excitement around my upcoming trip that includes xc skiing has me looking at Road Scholar trips. (A friend wants me to join her on a Road Scholar trip and this may be a way to choose one to take).
For years, my ex and I planned vacations around snorkeling and our carryon bag was a snorkel bag with swimsuits, towel, etc.
A long ago ex planned every vacation around golf (which is one reason she's an ex).
I know some Fodorites travel for opera.
I read about people who travel hours to a new city to buy a Hard Rock tshirt from that city.
Someone I know is part of a group that plans meetups to ride roller coasters.

Do your vacation had a similar/ ongoing "theme"?

(Not sure "theme" is the right word, but it's what I'm going with).

Food

Not really. We did drive Route 66 which is probably the nearest we'll get to a theme. Bluesroute would be good too if we had the money/inclination.
Oh and we started going to La Palma because that's where our dog came from.

Cheap airfare.

Where is it? I googled, Canary Islands, but know nothing about it.

LOL! Good reason! That's how I ended up in London on the last trip. (but point sale, not $)

Can you believe my flight into JAC was only $400?!

I look for dance fitness everywhere I go. But I do not plan a trip around it exclusively. Rather any place I vacation, I then find local events, teachers, dance studios, zumba classes, gyms and fitness centers, free hula, salsa fest, whatever... and participate in those.

Always where we can get the most for our travel dollars.

Westernmost of the Canary Islands, very green, volcanic, high, black beaches, snow occasionally, beautiful dogs, scenery, sunsets in that order, dark skies and telescopes. Only small - you can drive around it in less than a day but (at least last time we went) still a little bit of paradise on earth.
It's the one than some claim will fall into the Atlantic and send a tsunami across the Atlantic to wipe out the East Coast.

I just go wherever I'm in the mood for at a particular time. That's why I don't like to plan far in advance. I usually just book when the mood hits me and before I change my mind.

That said, when I go to Italy I do like to look for cooking and language classes.

BTW, Road Scholar runs the XCountry skiing weeks at Craftsbury, VT if you're looking to pursue that further. (At least they did when I went about 5 years ago).

Yes, I saw that! I am very interested. I'm going to wait to see how the xc ski part of the next trip goes and then suggest it to her. I saw they had other side focus features, including yoga, for some trips and she loves yoga. I think this may work as a trip we may be able to take together!

Did you enjoy the trip?

It depends on what I'm in the mood to do. Do I want to relax on a beach, explore museums, enjoy nature? However, where ever I go involves good food and fun.

I did a modified Harry Potter theme trip in London 2 years ago. If my grandkids had gone as originally planned it would have been full blown Harry Potter. It became more of a literary themed trip, we walked up and down Charing Cross Road looking for number 84 and went to the Docklands to see Call The Midwife locales.

I have done one Road Scholar trip and have one booked for San Antonio this October. They are a great organization, I think you get your money's worth, I think you'd enjoy it Starrs.

With one exception, we have not, although we sometimes travel for an event (ex. NY for the US Open, New Orleans for JazzFest). The one exception is major league baseball parks.

We do try to take advantage of whatever would be a local "theme" once we're there however. If we're in the south, we're going to eat barbecue. If we're in Florida, we're going to hit the beaches. If we're certain locations, we'll hit a bunch of Revolutionary and/or Civil War battlesites. But we don't initiate the trip around those things.

I had not really thought about travel and themes, but lately we have planned several around life events. This summer we will be in Kauai for our 45th anniversary with kids and grands. In September we are returning to Tuscany after a friend’s big birthday in Rome. So plan it and we’ll come?

While not into xc skiing anymore, we did have a good experience with Road Scholar on a trip to Santa Fe a few years ago. And we were going to go to Ireland with them last fall, but our trip got cancelled several months out due to low enrollment. Since we had already booked our airfare, I ended up planning the trip for us, and it worked out quite well.

For a long time while we were working, I would talk my relatively non-traveling, Atlanta Braves-loving DH into trips to various US cities because of the allure of major league baseball parks.

Now that we're retired and have been to games at most of those parks, I lure him to various locations because they have great geocaches. Actually, there are great geocaches all over the world but I show him that there are plenty of good ones in the places I want to go. Geocaching has been a great hobby in retirement.

Way back in the 80s, when it was called Elderhostel, we were at a motel pool in Colorado and had the best time talking to two older couples. They were on an Elderhostel trip and I loved the concept. They took classes during the morning and had the afternoon "off" to explore - or play in the pool all afternoon. I looked forward to getting old enough to go on a trip! My friend takes one at least once a year. She just got back from one in Philly. I picked her up from one in Asheville for the afternoon to took her to see the Biltmore decorated at Christmas. It's just been a challenge to find one that works with our schedules. She just took an early retirement (medical) so her schedule is far more flexible. She's mentioned Iceland so that's a possibility. I want to go somewhere I've not been before. The xc ski trip may work. Iceland could too. I need more vacation time!

Good to hear how much you enjoy them! I was at the DeSoto in Savannah at the same time another Fodorite was there on a RS trip. I noticed all the name tags in the lobby. Later he shared on the forum he was there on the trip. We were probably within feet of each other and had no idea!

Once had a colleague whose goal was to have visited every single pro baseball stadium in America. When I knew him, he was well on his way with his total visits. I'm pretty sure that he succeeded, or will very soon. He just retired.
I am done. The list.

Always.
Last trip to Spain theme was; "Movies from my childhood".
Cordoba and Almeria.
Lawrence of Arabia; Duck, You Sucker; The Good, the Bad and the Ugly.

Accidentally, stumbled on the "Mar de Plastico" locations as well.

Previous one was mainly: " Lighthouses I saw only from seaside"
The coast of Galicia, from Vigo to Ferrol.

Fisterra was a must.

I decide what I want to see and then where to go to see this.

Every travel has a new "theme"

For example, if I want to go on a Safari, I then decide where that Safari should be.