Correct usage of lftp mirror --older-than
it should be
--older-than=now-5minutes
from man lftp
For options --newer-than and --older-than you can either specify a file or time specification like that used by at(1) command, e.g.
now-7days' orweek ago'. If you specify a file, then modification time of that file will be used.
from man at:
You can also give times like now + count time-units, where the time-units can be minutes, hours, days, or weeks and you can tell at to run the job today by suffixing the time with today and to run the job tomorrow by suffixing the time with tomorrow.