>> I am using cat to capture video from VHS tapes, saving the files as mpegs
>>  and don't want to baby sit things. How can I launch cat with a
>> predetermined ending time without having to use cron?
>
> cat &
> catpid=$!
> sleep 3600
> kill $catpid

process ids do get recycled, so that could bite eventually, safer to
key on the job#, not sure how to fetch the job# of a job you just
launched, unless it's a fresh (sub)shell and therefore %1:

(cat &
sleep 3600
kill %1)