your stamina (1 shot guy or MSOG), individual tastes (like variety or stay with ATF), etc.

Let me add a 3rd option which would be to see two different ladies for 1 hr. each.

Tough question to answer.

For example, some providers may ask for 500 for one hour but 800 for two hours.  So from a pure $/hr perspective, the 2-hour session once a month may be a better deal.  But it all boils down to personal style and preference, really.  The 2-hour sessions work well if you don't want to feel rushed, like MSOG, want to get to know your provider better, etc.  The 1-hour sessions can be better if you're one-and-done, not much for chit chat, want to explore more providers, etc.  And those preferences can vary depending on your mood.  Sometimes I'm in the mood for a shorter session and sometimes I'm in the mood for a longer one.  To each his own and variety is the spice of life.

not necessarily with the same girl.   I'm pretty much a one pop guy, so an hour of play, a pop...  knowing my body, I don't let her take me too far, too soon.

At least in my humble opinion. I rarely do an hour anymore.

For me it depends on my mood. I would probably go for the two 1 hour sessions. That way it gives me more to look forward to and I could spread it out and only have to wait about 2 weeks for my next time versus having to wait a whole month.

Becoming a reliable regular with a lady will typically earn you a discount, usually reflected in longer, relaxed, unrushed sessions.  So you may only 'pay' for 1 hours, but find she wants to spend 1.5 or 2 hours with you.

I'd also go for the 2x 1hr if you are looking at 2 different providers, and/or different providers each month, because you double your chances of having a great time.

To me the 2hr session is for when I am really busy and haven't been able to see anyone for a while, and am repeating with someone reliable....I.e, when I have more money than time.  It's also good for providers that already owe me money, to work off their debt.