I've looked at the promotion possibilities and they are generally based on number of posts or likes or length of time since registration. These don't really suit this promotion criteria as I may have a user who has made a lot of posts but hasn't been around for several months. Similarly I may have a new, active user who hasn't made a lot of posts yet, or another user who visits the forum regularly but doesn't make any posts.
Ideally I'd like a promotion that works along the lines of:
If user has visited in the last 30 days and has made X number of posts during that time then promote to group Y
I've had a look at How to extend user criteria (for use in trophies, upgrades and notices/notifications). I'm not sure if this is possible using this or, if it is, it may be rather complicated to achieve (for me anyway).
So, can this be done? Or is this something that should be suggested to extend the default trophy/promotion criteria?