Nothing is set in stone, so a person
can get a reading whenever they feel they need one, even within 24 hours or less. There are no rules that say they can't. But I, for one, pretty soon get a little annoyed if they seem stuck in a rut and keep asking me the same thing. I don't mean I get annoyed with that person in particular, just with whatever it is that keeps them stuck in that rut. Usually it's relationship addiction, in my experience.
The way I handle it is---if it becomes clear that they're truly stuck, then I help them rephrase their question or re-direct their way of approaching the subject. In my past, I was a relationship addict myself because I had no self esteem and only felt worthy, loved and worthwhile if those feelings came from outside of me---in particular from a partner. When caught up in any addiction, try as one might, a person can't just rationally think their way out of it. If they could, there wouldn't be any people addicted to anything. First they need to be convinced that what they're doing is addictive and is going continue to the depths of hell if not remedied. Very often, that takes a lot of knocking their head against the wall.
It takes what it takes for all people---they're not going to "get it" just because I get annoyed with the same old questions and think "sigh---here we go again." And making a rule that I'll only give readings at certain intervals won't change them---all that does is just keep me pacified that I don't have to go "there" again with them.
You're the one who can decide how often you need a reading and if you feel you need one, then seek one out. If the one you often go to says it's too soon, it's your option to find someone else to read for you if you want to. If you're reading for yourself then of course you can read all you want on whatever topic you want. If you're doing readings for others and you want to set limits on how often a given person sits with you, that's your call and you can set limits or not, as you see fit.