When I started running marathons I waaited for 6months to do my second one. As I trained over the years I could do one a month without too much trouble. Finally I started training for ultra marathons and could do more than one a month.
I hope this helps you.
I have a lot of experience if you'd like to be in touch.
Other people asked questions on various topics, and are still waiting for answer. Would be great if you can take a sec and answer them