I should start logging some of my ideas earlier so I can do more 'told you so'. I've said in some places before that leveling time in mmorpg is primarily for the sake of subscription money. It's how the company makes their money. But someone who plays an unhealthy amount gets much farther ahead than someone who plays short, enjoyable bursts.
FFXIV tactics has a spin on this to simply slow down and stop you leveling after a certain time, so your not ahead of a predetermined leveling shedule.
To me its always starkly appeared to be the competing interests of making money and players wanting fun now.
Years ago when I played wow I thought of the idea of being able to wander out of the tavern, slay just a single monster, then waddle back inside and RP or log off, and for that first monster every day you'd get say 100 times the XP, but trickled out slowly to you (online or off). So if you didn't want to grind, you didn't - slaying a single monster would be an achievement. But if you killed more you'd get both.
That's another way, probably more towards player fun now. There are lots of ways to implement it, all with their own nuances.
Anyway, here's the video on it, where they are more honest about the behind the scenes than I would have expected. Though the bit at 4:53 is a bit rediculous 'If you really think about it, it works!'. How a game works is that it's fun. So it's like saying 'if you really think about it, it's fun!'. No, things don't become fun if you think about them real hard! However, thinking can dispell knee jerk assumptions of unpleasantness. However, the human brain is predisposed to work in extremes, either majorly pro or majorly dismissive. It has a hard time sliding the gear shift back to nuetral.
Oh, did I mention a video?...