I've been using a homebrew XP system of my own that grants levels approximately every 1.5 to 2.5 sessions. We've had 30ish sessions and the PCs are around level 15. I'm fairly happy with it.
I suppose it depends on the story that you want to arise from your campaign. If you have a ton of material that you want to explore, you could slow advancement. If you have have a fairly tight amount that you don't want to pad with filler, I could see increasing advancement to as much as 1 level per session.
If you want your campaign to run to level 20, at 2.5 sessions a level that's around 50 sessions (you get level 1 for free, but presumably you want to give the players a few sessions to enjoy level 20). If you don't have 50 levels worth of material, it's probably better to accelerate advancement than to add filler (IMO).
Yeah, I am running a Princes of the Apocalypse monthly game which is working well at ca 1.5 sessions/level; the pace is still pretty close to what the book expects (assuming not every bit of dungeon is cleared) and it works well with a fairly casual group doing the Epic Quest.
My Thule game though runs weekly and at 2.5 sessions/level should span 1-20 in a year, which is definitely much faster than I usually do.