Instead of mounting with the discard option, consider using the fstrim command to trim your SSD!
To manually trim your SSD, use the fstrim command.
stmiller@bruckner:~$ sudo fstrim -v / [sudo] password for stmiller: /: 60656586752 bytes were trimmed
This can be put into a cron job to be run daily, at 10:00 hours:
$ sudo crontab -e
Paste in the following and save:
0 10 * * * /sbin/fstrim / >/dev/null