I've never used canned fruit, but I've never left fruit in fermenter for more than about 5 days. It gets very mushy and white colored and starts to break down pretty fast. Maybe canned fruit is different, I don't know.
I usually do a 5-7 day primary (until the SG gets 1.010-1.020) and then rack to secondary. It stays in the secondary until the lees get 1/4" thick, or at least 30-45 days, before being racked again.