I have set up my first timer helper and it works great. The problem I have is that the “Restore?” option always unticks.
If I go in and edit the helper, tick the restore box and click update, it looks like it has saved but if I go out and in again, it is unticked. This means the timers are stopping when I restart HA.
I found that in order to have the timer set correctly (with restore set to true), all I have to do is
Create a new helper of type timer
Check restore (do not change the default time)
Create it
Now open this entity for updating (restore is unchecked)
Check the restore and set the correct time (in my case I had the time 1439:58:49 hours - and this workaround did not work xD, so I had to create the timer with the default value and then change it (20mins was OK).
Save it - done! Now the timer should work even after a restart.
(PS There was also a case where I set the timer to a certain value, started it and then changed the value. After that I could start and stop the timer, but it always used the old time - restarting HA helped).