How long do golden rod dehumidifiers normally last before they "burn out"

Don't know yet. The first one I bought was for my wife's new piano, now it's something like 35 years old. The second one went into my gun safe, about 18 years ago. Both are doing fine.

I bought mine used, 5 yr. ago. It' still warm.

Do power outages or surges affect them any long term?

I don't think there is much to go wrong with them. I probably have more power outages and power issues than most people. I live at the end of the road sort of thing. I've have several over 25+ years old and they still work.

Outages are no more hamful than unplugging it would be. It would take a massive surge to burn it out but that would be evident in the really short term, AND you would have so much burned out stuff the little heater tube would be the least of your worries!

I have had mine in place and plugged in for about 10 years and have had no trouble with it!

Mine has been in the safe for 12 years and still does it's job