I also drink a lot of iced tea even in winter, as well as coffee in the morning. I've never tried any of the OTC white strips; my dental hygienist had told me that they didn't work; I think she might have even said something about them damaging the enamel or something--I can't remember exactly what she said, but I just remember thinking that I definitely wouldn't do it.
But I've recently switched to a Crest toothpaste with extra whitening, and even though I've only been using it a few weeks, my teeth seem to be a bit cleaner. I used to always buy the cheapest toothpaste I could find, which was usually ultrabrite, or whatever CVS had a good ecb deal on.
I'm interested to hear what others say who might have used those OTC strips--the stains from the tea can get really ugly.