Today I am in my 90 day window.
I want to travel May 17th from Paris to Bergerac preferably routing thru Libourne rather than Bordeaux as the connection time is less.
I would like to leave Paris mid morning so that I get to Bergerac early afternoon.

I went to both sites to see what is available and here is where the confusion comes in.

The voyages-sncf.com site does not have any schedules. If I try earlier dates -May 7th is what comes up-but it is not an prem fare.

If I try on the capitane site only one train comes up routing thru Bordeaux, leaving Paris at 9:28 arriving in Bergerac at 15:30- (about 1 1/2 longer than if I route thru Libourne as shown May 7th).
This fare shows as prem, but the symbol IDTGV does not appear.

My questions are:
1. Should I wait and try and get an IDTGV train?
2. Am I confusing prem fare and IDTGV? or what is the difference?
3. Is 70.80 euro a good price to pay for a first class ticket from Paris to Bergerac
4. Why does only one train time come up on the capitane site?
5. Why does no train schedule come up on the Sncf site?
6. What should I do-book or wait?

Any hints to help me be unconfused greatly appreciated. Merci.

Why on earth do people keep obsessing about this 90 day window? Just wait a few days and the schedules will come up normally.

ID-TGV only serves major cities/resort towns. You can get one to Bordeaux, but not to Libourne or Bergerac.

You probably just attempted the voyages-sncf.com site too early in the morning as I am able to find the same schedule there as you found on Captaine Train.

The only train I see for that day is the 09h28 departure with the lowest fare at 42.40€. PREM fares have nothing to do with iDTGV fares, they are mutually exclusive fares. iDTGV fares relate only to iDTGV trains of which there are only limited numbers travelling to larger locations as kerouac mentions. PREM fares are limited in number and are available on regularly scheduled TGVs.

70.80€ is the only price available for Paris - Bergerac so you must decide if it is worth the cost.

One thing is sure, prices will not go down, they only increase as seats are sold and as any given travel date approaches. There is no advantage in waiting.

I just checked the schedules on that route for two days from now and for May 17th and indeed on May 17th only a few trains show whereas there are many showing two days from now so you probably just need to wait a few days for the full schedule to be released. For two days from now I noted an iDTGV fare on the 9:28 train for 67.10€ and other fares ranged from 85€ to 89€ on that same day. If I choose a date a few days before May 17th (I chose May 13th) I see a full schedule and fares as low as 32€.

I'll mention that the fares I was checking were second class fares, not first class.

ok, thank you, I now understand the difference between prem fares and iDTGV.
I was able to book a PREM fare, which was constantly changing as I was trying to figure it out.
Glad that's done!

FWIW, the actual schedule for release of all fares is not 90 days, it's 3 months, so depending on how many days in each particular month it may be a bit more or less than 90 days.

But you got it figured out, so all's well.