What if instead of failing to heat, it leaks instead, which is the more
common failure mode? And there have been lots of cases where a 10+
yr old gas heater suddenly leaked so bad that it flooded the basement
and caused thousands in damage. One has to evaluate what the
consequences of such a failure will do in their particular situation,
ie where is the water heater located and what will happen if it fails.
Somewhere in the 10-15 yr range is typically all you get with a gas
unit, which is what tivo guy has, while electric units can last 20 or
so. I got 11 years out of mine before it developed what I would call
a moderate leak in the middle of the night. When you consider a new
one that may be more energy efficient, plus a $200 deal, I'd probably
replace it now.