I have used the meg'* spray, and it was alright.. but wasn't as good as this cheapo turtle wax liquid I got. In the summer i'd apply it at least 3x/week. Used the whole bottle on the car, and the seats have improved incredibly since using it. However, I have also applied the stuff tons and tons of times. Probably a good 50 times. And for the few bucks I pissed at the bottle, it was totally worth it. I also have waaaay too much time on my hands, and get bored.
I've always thought you do it everytime you do a full exterior detailing [wash, clay bar, wax, etc..], which I do every other week. Again, I also have way too much time on my hands. Do it as much as you want or can afford. Can't hurt, as like with my car.. but you've gotta do it, otherwise your seats 'll look like **** in a few years [if they aren't already now]
'89 SSE - GX3 -190k, 155k on body - Back for another ride.