i can't shop now-return later just because of the nature of where i am. i'm at school 2 hours from Atlanta, where all the places i like to shop are, so on the rare chance that i get to go to Atlanta and buy something, i have to KNOW that i want it because i may not be back for 6 weeks (since a lot of times i work on the weekends). since a lot of return policies run out after 30 days, that becomes an issue.
but even before that, i wasn't really a returner. i hate feeling buyers remorse, so whenever i see something i like that i might want but am not sure, i have them hold it while i 'take a lap' - walk around the rest of the mall, grab a diet coke, look at some more things, and if i'm still thinking about it when all is said and done, i go back and get it. if it's something that i know won't sell out (a skirt at the gap or something) i'll usually go home and give it about a week if i don't love it.
i do that because at this point i've been shopping seriously since i was 14 and i KNOW what i like and what i'll wear and use. my mom says i'm the fastest trier-on ever because i don't do much modeling of the clothes in front of the mirror. if i don't HAVE to have it as soon as i put it on, i'm not buying it. she, on the other hand, takes forever in that little room...over 50 and STILL not comfortable with her personal style!