gas last less than electric, around here 10 years is good life. I
replace mine about that time.

new designs are much more energy efficent and if a flood can damage
stuff your better off replacing early.

WHs are realtively cheap appliances, divide purchase price by 10 year
life.... very low.

I prefer to pick and choose replacement time, after the one died
christmas eve during snow storm, 20 degrees and howling wind,
houseguests coming the next morning.