[smartmontools-support] Best way to only enable smartd with removable storage actually present?

[Dachshund Digital]

Best way to only enable smartd service with removable storage actually 
present?

I think the best way to do the above is via UDEV rules that start/stop 
smartd service when USB removable storage is added/removed.

But thinking what is the harm in letting the service just run all the 
time?  I does not seem to be a significant memory footprint, no 
significant load cycles, when no USB storage devices present.

The most efficient approach is of course the UDEV rules.  But is that 
overkill in this case?  Thoughts?

-DD