Because it takes so long to reach the highest level in prestige, I have an idea.
-They could run an event that grants prestige as a prize.
Type of event and amount of prestige given could be just about anything.
-Or instead of an event, they could make some territories with a certain out put of prestige. Like 100 prestige an hour while you hold said territory. (Just throwing a number out there). You get the idea.