[abusharif]

there is no automated function but u could do:

-fwm dbexport -f /root/myusers.txt
-cd /root; cat myusers.txt |sed 's/31-dec-2008/31-dec-2020/g' > /root/mynewusers.txt
*(first date is the expiration date, second date is new date to set it to)
-and them fwm dbimport on the newcreated mynewusers.txt file.

Try it in test enviorment first