I find it difficult to know exactly where in the song I am while playing this. There are a few long/drawn out riffs in the song, mainly the first riff and the middle section when jimmy page uses the violin bow. Basically what I have done for the section with the bow "solo" is divide it into three parts. I count 1 ee and ah 2 ee and ah 3 ee and ah etc. up to 8 ee and ah for the first part. Then I count 1 ee and ah through 8 ee and ah 3 times for the middle part. Then the last part I count 1 ee and ah through 8 ee and ah once, 1 ee and ah through 4 ee and ah once, and then five more beats. Please just tell me I'm stupid and that there's an easier way to go about this
How long have you played? When you play a lot you just get a feel for how long it's been. I won't lie though, if I was playing something live that had like 8 bars of the same thing with no variation... if I even slightly drifted off I'd be screwed.

Some people go

1e+a 2e+a 3e+a 4e+a, then they name the beat at the beginning and would continue saying:
2e+a, 2e+a, 3e+a, 4e+a, ... 3e+a, 2e+a, 3e+a, 4e+a, ... 4e+a, 2e+a, 3e+a, 4e+a, ... 5e+a, 2e+a, 3e+a, 4e+a

Basically making the first integer what the name of the bar they're on. Hope that helps.