How long can you grind?

I tried something new today while training. I just put about 6 little pieces of paper over the exp bar, enough so that I couldn't see it, and taped it up. I got the idea from earlier in this thread (I think) and it really did work. Usually I'm constantly looking at my exp bar and checking my exp/hr, but with this I just sat back and grinded without even thinking about it, which made it more enjoyable. I was also pleased to see I got 17%, and i probably would've gotten like 5% if I didn't do this

Sounds like something i need to do lol