Are you factoring in training time/costs?
I ran AD&D last year and had a great time with it. There's an interesting thing that happens during the low levels of AD&D:
Let's say you are playing a thief, and you have accumulated 1300 XP. 800 of which came from gold. This is enough to go to 2nd level.
Ok, so it costs around 1000 gp a week to train to the new level, and it requires a number of weeks according to the E, S, F, or P rating the DM assigned for "how you did during that level.."
So let's say we got "S" for superior. Thats'two weeks. Time to go adventuring again, because we are now 1200 gold short of the gold we need (to pay for training!) to hit 2nd.
So we go out and adventure again, and bring back 1200 gold. We also gain another 600 XP in monsters killed, or whatever.
Now we are at 3000 XP. And we just barely trained up to 2nd level. But we have enough XP for 3rd level! But crap, we're out of money. And it's going to cost us 3000 gold this time. And by the time we haul that home, we'll have enough XP to actually be 4th... And you know what happens to excess XP? You lose them!
You never get out from under this cap until like 6th, at which point the training costs start to become irrelevant.
Here's a table with the fighter from the actual campaign we ran: I always assumed a "2 week" training period.
Ok, and this also means characters up until this point will constantly be broke, having to pay it all into training. But that's kind of cool, actually.