I normally mull it over for a few days, if after that I still like it, then I go ahead and click "buy", call or go to the boutique. Unless it's something I really want (like the mahina) then I go balls out and buy it right then and there!
It takes me at least a month to be sure.
at least one month for me... couse they are not cheap bags and I dont want to be get upset after I get my new goodies.