For what purpose?
I mean, I have groups that have old members that haven't been in the *game* for a year and a half to two years, if not longer - they're mostly alt-groups, so nobody gets kicked. Why would they be rewarded, again? SGs were introduced way back when, before there were bases. There could be tons of inactive players getting years of "rewards." What would be the point?
It would be great if there were badge/bonus for group/player:
Each year of membership in group.
Each million prestige brought into group.