Hussar
Legend
Man you guys all level up fast.
I can't put it in terms of hours played, nor for that matter in terms of much else for each individual character as they come and go. I also don't run the same party continuously - we'll play one group, put them on hold, play another party, then go back to the first, etc.
All I can look at is the overall average advance rate of the leading characters in the campaign. And over the very long term in my various campaigns it always seems to come out at - give or take - about a level a year overall.
Individual characters can and do advance somewhat faster, particularly at very low levels getting from 1st to 3rd or even 1st to 4th in a year is not unheard of. But after that things slow down; and if lots of characters die and get replaced (or just get level-drained) the average level can stagnate or even go backwards a bit; replacements always come in at the start of the party's lowest level.
That said, while it's nice to bump now and then it's not the main focus of play for us. It's more like a pleasant side effect.
Lanefan
I know it's totally a personal taste thing, but, wow, would I not want to do this again. I've played in this kind of group and I find it very, very frustrating. In D&D, particularly, you need levels to accomplish just about anything. Spending a year of play time (which, for me would be about 130 game hours or so) just getting to 4th level is not to my taste.
Then again, I tend to see campaigns which last about 12-24 months at best, so, we shoot to tell the story over that period of time.