Not enough information - enjoyable in what sense compared to once a week?

Do you mean that your ATF *treats* you better if you see her once per month than once per week? Seems more interested? Sex is more intense? Service is more thorough?

That is true of some ladies. Many are just as into variety as some hobbyists... and absence does make the "heart" grow fonder (and the sex more piquant) with *some* ladies

(OTOH with some ladies the more often you see them, the longer you know them the *better it gets* - now *there* is true "ATF" Potential)

Or do you mean that you feel bored with her if you see her once a week? Some clients are like that. I am with the overwhelming majority of providers. For me a good "regular" visit is three or four times a year with most ladies...

Either way I suppose that if you enoy her more, less frequently, then that is the appropriate strategy for you....

Gives you time to refresh the neurotransmitters so that the experience seems more fresh.

Also gives you time for things to happen in each of your lives so that you have something to talk about, assuming you do some talking.

Sessions with other ladies in between also are useful in preventing the pair bonding mechanism from working and that can be kind of subtle.

Whatever works, man. There aren't any rules in this hobby.

I usually stick to the same session length...  too much frequency can make the relationship stale & some anticipation is great.  IMHO, going exclusive or nearly so leads to the providers semi-taking us for granted.  I rotate a few (2-3) Favs...  occasionally I'll see someone who has Fav potential.  
It is V nice to catch up with a Fav lady...
skb

Maybe it is the length of time in between that makes it better?

For me that depends on how long the session is. I find that the more time I've spent with a lady of a certain skill level and attractiveness, the hotter and more satisfying the experience (for both of us I think).
So if it's just an hour, once a week for sure just to keep things heated up (unless you feel like it's stagnating or unsatisfying)...if it's a 3-hour date, maybe once a month would do it. But that's just me...I have friends who rarely see the same lady twice, let alone establish a 'regular' thing. They like that hit-n-run rush. That doesn't work very good for me, my first hour date many times is 40 min of touchy feely 10 min of fking and then 10 min cleanup & kiss/hug goodnight. Then the next date will be 2 hrs solid fking. Then she moves in...(just kidding)
So I guess this is another of those 'personal preferences, YMMV' things.