Be careful if you add sugar, so you don't use the same amount as you would for bottling.
I've recently started putting my beers on 20 psi for 24 hours and then backing back down to serving pressure (~8-10 psi). Since i mostly drink english beers that don't require lots of carbonation, this seems to work well.
Also, you asked about aging the beer. I've discovered what most people who keg say, which is you get to a point where you have kegs aging and waiting to go into the keezer when you kick one. I've got four in my fridge (it's full, no more can go in) and i'm still planning a stout and a bitters with the idea that they will age and go into the rotation when i'm finished with some of the other beers. This way you also don't have to wait on one to finish fermenting and you wont run out of beer.