SkyHigh:
Your observation is only correct on some paint brands, but you've hit on a far to common mistake made by all us hobbiest. We tend not to read the lables on the products we use. If the lable says "recoat in 1 hour or 5 days", than by goodness, ya better be watching the clock, or its crackly city.
However!
Krylon has an entire line of spray paints with a "RECOAT ANYTIME" forumla that allows second, 3rd and so on coat whenever you want. This stuff is fantastic!
It is most important that you read the lable on any spray applied product you pick up. Primers flash off much faster for many reasons and may be sanded, recoated and resanded the same afternoon. It's usually the top coat colors that will kill you if you don't read the lables. Personally I will not buy any spray paint product that doesn't have the "recoat anytime" lable for general sport model painting. Krylon also has an excellent line of florescent colors.