I can think of a couple of reasons this may be.
I don't see where you are from, but if it was cold when you started with the MES, it would be "on" more heating up, so would generally smoke more if you had wood still in it. The warmer it gets outside the less it has to turn on to keep to temp and so would not smoke as much maybe.
Another possible is that when you were "new" with the MES, you were a lot more hyper about it and were putting wood into it more often than every hour. I find that sometimes I can go an hour with a big chunk, but generally it's more like a half hour if I'm using chips.
And that brings up another possibility. Maybe you were using bigger chunks of wood before so they lasted longer than the wood you're using now, or maybe it was greener/wetter than it is now so lasted longer.
And of course, it could also be that as you've been smoking more, you've developed more of a taste for smokier food just like it seems that people that eat peppers tend to like them more and somewhat hotter as time goes on.
Just letting my mind wander (gets easier and easier every year!
), you could also try using a different wood. Mesquite is pretty strong though. But you could try hickory which is pretty robust and can be pretty smokey without making things taste bitter.
And...have you changed your rub? That could also be something to look at.
I'm sure there will be more folks to help out too but maybe some of these will give you an "oh yeah, that might be it". Good luck and keep on trying it!
