Back in the 90's... I ran a FL-1A on a 400M 2-bbl truck for 30,000 miles (3X OCI's) and when I cut it part it looked good.
Other vehicles I have seen in the last 40 years have had more miles on a filter than that.....
A CLEAN engine will stay clean.... and the filter won't have to catch hardly anything.
On a modern engine, I dare say 20,000 is VERY EASILY achievable,
and I sincerely doubt 50,000 on a good filter would hurt anything as long as regular oil changes happen.