It is 60 days for age-related removal, but it may not be done with daily granularity (i.e. once a week or something). There's no limit on the number of events, though.
"On two occasions I have been asked,—"Pray, Mr. Babbage, if you put into the machine wrong figures, will the right answers come out?" I am not able rightly to apprehend the kind of confusion of ideas that could provoke such a question."
- Charles Babbage