Hi,
Could you be more spefic? Filewatcher Jobs are really there for that purpose you just mentioned.
So, what do you want to do when the time period is over? Want the job(s) to go to faillure? Want to get an alert? Or, you don't want any alert?
Anyway, to let the job run for an x amount of time you should give the job a max run time. This is the time calculated from when the job switched to RUNNING. NOw, you can check the box to let the Job fail or not ('Send alarm if this Job fails').
Cheers,
Danny