Kegging less than 5 gallons question

I have about 4 and 1/2 gallons in my first keg. First question is will it take less time to carb up just right? or will that not make much of a difference. I was going to test it at 3 days and see if its carbed enough.

Also, before I turn the PSI down to serving PSI do I need to relieve any of the pressure by pulling up on the relieve valve?

4 1/2 or 5 gallons will likely carb a the same rate...more or less. If you are force carbing at a higher pressure, yes, you will need to reduce to serving pressure by venting the keg.

3 days is likely to show no difference unless you are burst carbonating at a very high pressure, which i do not recomend.

people always want their 25 pound turkey cooked and ready to eat in 15 minutes. it just doesnt work like that.

However, you can easily quickly carb without over carbing by simply set it at the desired pressure (12psi for example) and then rolling the keg back and forth for 10-15 minutes or whatever works. That way, it's doing the same thing without the possibility of over carbonation. Just make sure it sits for a few hours to let everything settle inside the keg. I did this method the night before thanksgiving for my pumpkin. Set at 12, rocked it for 15-20 minutes, let it sit over night, tested in the morning and poured a perfect carbonated pint. AWESOME!

With that said, if you have time, the set and forget method is probably the best though. Lots of ways to get to the same place.