It's still vulnerable to a Reload Timers (which is a required operation if you ever create another timer and it will happen automatically if you create the new timer via the UI) and, of course, a restart. The version I posted above survives a restart and is more concise; it's simply a more efficient design pattern.
However, if you are adamant about using a timer, you might be interested in implementing the following system for restoring active (and paused) timers after a restart:
NOTE
The following simple tutorial explains the process of transforming a simple automation, vulnerable to restarts, into one that can perform the correct action even after a restart: