Type of Burner for brewing

I have heard that 65,000 BTU is about what I should be looking for in a burner. I plan on doing 10 gallon batches.
Is there a difference in the PSI for the regulators?
How long / how many brewing sessions does a typical propane tank last?

Thanks
Josh

10PSI regulator should get you 55k BTU's. 20PSI regulator should get you about 185k BTU's.

55k BTU's is great for 5-gallon batches, and I have little doubt that it would work for 10 gal batches also, just be slower, but I would think that you might as well go for a 185k BTU burner while you're at it - it'll speed up reaching a boil, and there's no real downside other than the initial cost, as you'll be dialing it down to the same pressure for the duration of the boil anyway, regardless of which one you use.