Simple answer: yes - long running Perl processes are definitely possible. Long answer: yes, but consider what might happen if your long running process is started while a previous run is still happening. You can avoid this using lockfiles or pid-files, for example. You might also find Proc::Daemon useful to get your program running without a terminal (although if you use cron to launch it you won't have to do this).

For an example of a long-running Perl daemon you could look at Krang's scheduler and FTP daemons.

-sam