Similar thing was previously discussed here:
But I wouldn’t consider the 10x recommendation to be any kind of an exact value, more like a rule of thumb, actually. In the long term, the reviews accumulate very slowly, and other factors, such as changing life circumstances and progression in the learning material begin to play a much bigger role than any theoretical limit anyway. And as far as graduating cards goes, I, for example, have many that already grew to intervals > 20y, and that I don’t expect to live long enough to successfully review more than a couple of times more. This makes them practically graduated in a natural SRS way, without putting any arbitrary upper limits.