I feel that there are many different approaches that the developers could have used. Cumulative total of months to have received boosts, cumulative total number of individual boosts over time, etc.
The currently employed method has become this manipulative popularity contest that will no doubt cause pressure on communities to keep spending to maintain perks. Not "unlock" them, but to "maintain" them.
This also means that smaller communities, no matter how loyal or how active they may be, will likely never access higher tier perks.
I think there needs to be more to be done so the smaller communities can also gain benefits, rather than causing rifts between and within communities themselves.