There is a journal editor who keeps sending me review requests. He sends a new one shortly (a couple of weeks) after I return the previous one. I tend to accept because they align quite well with my expertise and I want to stay in good terms with this editor, who is a prominent figure in the field. I am a slow reviewer, but tend to give quite detailed and comprehensive reviews (compared with what I usually get for my own papers), and I guess the editor is happy with the quality of my reports, otherwise he wouldn't keep asking. However, I wouldn't mind if he asked less often. After all, this is only one journal and I also get review requests from other journals.
I have no experience as editor, and I am wondering if there are any best practices from that side. Is it common for an editor to keep "milking" that reliable reviewer? For those of you who have editorial duties, do you have any limit on how often to ask? Once a month, once every two months?
My intuition tells me there's a risk the reviewer gets tired of getting so many review requests from the same editor and the editor may end up losing that valuable resource.