I see no problem with mechanical timers when the power goes off to warrant the extra money for digital. All I have to do is spin the dial around to correct time .. takes a few seconds. The "pins" or "blocks" stay in the same "timer" positions .. if they didn't then it would be more of a problem. I spend way more time resetting all the digital clocks in the house .. like the microwaves, stove, etc.
I guess if the power went off in the middle of the night then the lights wouldn't come on at the correct time but I figure a few hours shouldn't hurt anything.