@jayk34 - not to confuse things, rather to help you make an informed choice for what will work for you(and forgive me if you already know this):
You don't
have to serve at a different pressure to that which you use to carb your beer. For example, I set my line length based on the pressure used for carbonation (as has already been mentioned above) and I don't touch my regulator until the keg is empty (in fact, I don't even fiddle with it until the next keg goes on come to think of it).
If you serve at a lower pressure, your beer will become less carbonated as time goes on. You could bring the pressure back up between sessions, but that seems a lot of effort, in my opinion.