For me, there is no one-size-fits-all answer. I am looking for a long-term arrangement, it could be 6 to 12 months. My offer is not set since it would depend on who the client is, where he lives (close or far from me), do we always have to travel to see each other, whether are we travelling together often, sometimes or never, the budget, his needs and wants, if it's sexually-oriented or company-oriented, etc. It could therefore be an exclusive or non-exclusive one, and this of course would depend on many variables.
I expect this kind of offer to reveal itself organically; I believe an arrangement will become obvious for both of us after seeing each other a few times, more likely to happen with someone who books extended appointments, and given we have excellent chemistry.