It is different for every person. My experience went something like this:

I started at 10NL/25NL. My BR for that came from SnGs. I played at 25 NL what seemed to me forever because I was two tabling and getting used to online poker cash games. After maybe 35k hands of two tabling, I had the BR to move up to .25/.50 and got used to cash games online. I began four tabling and 50NL played a lot like 25NL plus I ran hot and only after about 15k hands I had 30 buyins at 100NL and moved up.

100NL was a complete different game than anything else I played and I had to stay at 100NL for a very long time and relearn the game to be able to beat it. Not sure how many hands I did there, around 100k ezily. 200NL is also different from 100NL and you have to learn and improve a lot from 100NL to be able to beat it.

Basically, the higher you go up, the more time and effort you have to spend at a certain stake to get good enough to move up, which results you doing more hands. This is true atleast in my experience.