I had the same problem in EQLive. I don't know about you, but I know exactly what the problem was for me.
Low levels:
Spend an hour at the newbie log in Nektulos killing wolves, beetles, spiders, and decaying skeletons
Spend an hour at the Pyramid in Nektulos killing decaying skeletons, skeletons, and the occasional zombie and bigger snakes that wonder too close.
Spend an hour at the Monolith in Nektulos killing skeletons, zombies, mummies, and the occasional giant spider, tree snake, or bear that wanders too close.
Spend an hour or 2 at small Orc camp in EC killing orcs.
Spend 2 - 3 hours at the big Orc camp in EC killing orcs.
Spend a couple hours at the small Dervish camp in NRo killing dervishes
Spend a couple hours at the big Dervish camp in NRo killing dervishes
Spend a couple hours at the beach in Oasis killing snakes, pumas, caimans, crocodilles, bigger beetles, and dry bones skeletons.
Spend a couple hours at the Orc Highway in Oasis killing different Orcs.
...
...
When you get up higher, like level 32-40...
Sit on your ass on the edge of OT while 1 player goes out to pull 1 random mob at a time and your group kills it. And repeat this over and over and over for hours upon hours at a time.
For me the problem was that the game suddenly became extremely repetitive and boring.
At the lower levels you and your group had to find a camp and split it up and kill things as they spawn, some times you can barely even keep up with it. It was actually fun. But it is quite a bit more dangerous. At higher levels the experience penalty for dying was far too great nobody was willing to take the risk so everyone played the game so friggen boring just sitting on the edge of the zone pulling 1 mob at a time. That is what always made me lose interest in the game. My highest level character was... somewhere between 44 and 46...