This is an article describing my experiences with Leatherique and is meant to be read after you understand what the stuff is, how it works and how you use it, which you can find out from their website.
Leatherique is made in Florida and you might note in their instructions that there is a step that says "leave the car in a warm place, but not in direct sunlight, with the windows up". That's great and all but, I'm in Canada - our warm day is the second tuesday in August. So, for the rest of the year we have to make other arrangements.
Now, just putting Leatherique on some leather will not do a whole lot. The two important details from the instructions are to a) cover it with plastic b) let it get warm. It needs to sweat to work, and by work I mean penetrate the leather completely.
If you live in a warm climate the latter should be no problem for you. As for the former - covering the leather being treated is not an option but poses no problem in northern climates. Which leaves us with just the heat issue.
You don't want it to get too hot - around 90 is about right. 110 and up won't hurt but it's really not going to work much below 90. It only needs a few hours at this temperature although this depends on the initial dryness of the leather.
If your seats aren't too bad, then simply using a hand held air dryer on the plastic covered leather will do the trick, but obviously you will have taken the seats out and brought them indoors to do this; it's not like you can use a hair dryer outdoors in a Canadian winter. You'd look silly if nothing else.
If what you're trying to revive is in need of more than a periodic treatment to preserve suppleness and falls more into the "this seat is fried" category then you'll want to use more Leatherique and keep it warm and in plastic for a couple of days.
In my case I'd put my seats in a very small room and slowly over a couple of day kept raising the heat. When it got to 100 the effect was quite dramatic. Literally overnight the seats had turned into the butter soft supple leather I was expecting. You see, to work properly Leatherique needs to work it's way all through the matrix of fibers that is your leather. For this to happen they need to open up - and this is what the heat does for you. I tried various things before this, but this is what I recommend. Any semi-sealed small room that you can raise to 100 degrees Fahrenheit without getting the source of heat too close to the leather will work just fine.
Another handy but totally related tip is an answer to the question "how do I soften or clean my leather watchband". After wrecking quite a few sitting them next to a fire or a heating duct utterly fossilizing them, I hit upon the idea of sticking them in a small, sealed plastic bag, dousing them very liberally in Leatherique (but not to the point where they're actually sitting IN liquid) then putting it in your pocket. 1 or maybe 2 days of this and it can bring any leather watchband back to life. If you use the Leatherique cleaner after word (and this is not really an option) you can get rid of that funky dirty watchband smell, too.