you can get by without leaving the co2 hooked up no problem. I switch my tank between various kegs, I can pour a whole buncha pints from a keg before giving it another shot of co2, I just insure that after the drinking is done that there is around 10psi when left to sit.... if you have no leaks it will hold the pressure without being hooked to the tank.
Aside from conditioning factors, carbonation is carbonation whether it is done with force or over time at lower pressure, it is just a matter of dissolving an amount of co2 in the beer. Cold temp and pressure helps the co2 dissolve quicker, as well as agitating the keg. Lately I've been doing it out in 30 to 35 deg temps overnight in my garage. I kegged a stout yesterday and just had a glass for lunch, it is wonderful. The day before I did a black IPA and was drinking that yesterday.
I've only been kegging for a few weeks, once you play around with force carbing a bit the mystery disappears.... just keep it as cold as possible and after about 36 hours take a sample every day, be sure to release the pressure first.