Thank you for the clarification.
The easiest way to accomplish what you're after is to run your script with the loop within a wrapper like the
timeout command from the GNU Coreutils package.
root@coraid-sp:~# timeout --help
Usage: timeout [OPTION] DURATION COMMAND [ARG]...
or: timeout [OPTION]
Start COMMAND, and kill it if still running after DURATION.
Mandatory arguments to long options are mandatory for short options too.
also send a KILL signal if COMMAND is still running
this long after the initial signal was sent.
specify the signal to be sent on timeout.
SIGNAL may be a name like 'HUP' or a number.
See `kill -l` for a list of signals
--help display this help and exit
--version output version information and exit
DURATION is an integer with an optional suffix:
`s' for seconds(the default), `m' for minutes, `h' for hours or `d' for days.
If the command times out, then exit with status 124. Otherwise, exit
with the status of COMMAND. If no signal is specified, send the TERM
signal upon timeout. The TERM signal kills any process that does not
block or catch that signal. For other processes, it may be necessary to
use the KILL (9) signal, since this signal cannot be caught.
Report timeout bugs to firstname.lastname@example.org
GNU coreutils home page: <http://www.gnu.org/software/coreutils/>
General help using GNU software: <http://www.gnu.org/gethelp/>
For complete documentation, run: info coreutils 'timeout invocation'
In the end, it will be much easier than writing your own timeout function, which shells tend to not have builtin.