My thinking on this topic has to do with time. If someone has an active sub for 6 months and the majority of the player base is far exceeding them it makes sense to give something to help the keep up. I am a big fan of offline time equal increase gains of some sort. If someone is logged off for several days give them 3x gains for a 2-3 hours. Maybe more, you need to do something to help people with less time keep up to retain them.