I use timers here and there in Domoticz, however I experience them unreliable many times. I guess Timer, as it named, is a function that counts down the set number of seconds and then fires. Yes that's fine, however under an active Timer session Domoticz may run into troubles like power loss, crash or a user update of Domoticz! Yes more or less that may happen. So in that situation the Timer function is altered and a 2KW heater for example that was meant to turn off after some time will keep being on forever or until the user notice and turn of it manually... can be expensive, and hot!

My suggestion to a big improvement is that Timers method is redesigned in the way that when a Timer is activated the "Time" it would fire is calculated and stored in the Database instead of "counting to zero", and as soon it is fired/time have passed that Time is removed from the Database. A "Time" based Timer instead of keep counting would be best in stability, reliability and even less in CPU time I guess?
I experience also an electric towel heater I set to start at 06:00 every with Timer delay OFF of 32400 seconds (9 hours) don't turn off next day after upgrade of Domoticz, even at 11 hours it is on, some kind of bug.
Maybe I am wrong in my conclusion in system functions? I am not a programmer so I am not able to revive actual code methods

Thanks for listening!