Block heater, timer, and parked for a while

I have the extension cord that I plug my block heater into on a timer, so it kicks on at 3am and off again after I leave for work, but on the weekends or days when it doesn't get driven, is it OK for the timer cycle to kick on? I've been doing it but is it excessive heating/cooling to let the cycle run?

Thanks

 

It's not doing any damage to the truck, but why pay for the electricity when you don't need it heated up. Only plug it in when you know you need it the next morning.

 

OK, thanks for the input. I usually try to leave it unplugged if I know it's not going to be used, but sometimes I don't know if I'm going to be going anywhere or not, so I'd rather have it warm than cold.

 

Plug

I must say, the timer is a good idea.waytogo

 

Christmas time is a great time to get them too - they're about $10 for the 1000+ watt 3-prong timers