We will be in Eastern Sicily next week for 8 days. I booked 2 nights in Lipari since we have never been to any of the Aeolian islands. We arrive about 2 pm Tues and leave Thurs morning. Weather permitting we plan to spend a few hours cycling around the island. I have 2 questions: should we try to see another island too? I believe Vulcano and Salina are close by, so could go for 1/2 day. Or just enjoy Lipari?
Also can you book boat excursions for a couple of hours? I have seen ads for the longer excursions but am wondering if a shorter boat trip might be an option at all. Not sure if its worth it at this tome of year (no swimming). Tx for any advice!

There is plenty to see in Lipari for the time you will be there so you won't be bored. I spent 5 days there but it was in September and spent a lot of time swimming. Still, it's a lovely island to explore.

On a previous occasion, I went to Vulcano and Lipari on a day trip from Milazzo. Vulcano was interesting for the sulphur baths but otherwise it was stiflingly hot and I recall walking around with little shade anywhere and just a few shops to look around. It was also smelly due to the sulphur and I recall thinking that an hour or less would have been more than sufficient there. I couldn't wait to leave. Of course, it was in the summer so it should be much more comfortable this time of year and if you're interested in the baths, then you should go.
I can't recall if I've ever been to Salina but if you can go there for a couple of hours, it might be worth it.
I do recall a number of small boats in the Lipari harbor and some tour companies so you should be able to arrange something to suit your interests and can find out more when you're there. Enjoy bella Sicilia!