Once you get set up with a few kegs, I think the best way is to keep it at serving pressure all the time, but if you only have a couple of kegs, sometimes you just can't wait for the week to gas it up, but you always risk overgassing the beer that way.
I am too lazy to keep adjusting the gauge all the time, so now I just try to keep ahead of schedule with my beers, to make sure they have at least one week to gas up before being used, but find it is just right after about 10 days on serving pressure.
There is a calculator by Crozdog under articles in the menu that will work out your serving pressure quite accurately, given the beer style, temperature and line type you have, to make things easier to work out.