As long as you don't start it while its running, I see no problem.
The obvious problem is using one timer for multiple things makes it
easy to overlap, especially if you start it in multiple triggers.
You should use conditions to check if the remaining time is 0.00 and if yes, start it again.
Though IMO I see no reason to not use multiple loops as long as you turn them off
when you aren't using them. You can easily check when the loop isn't being used, especially
if you use it to pick units.