It's the most common problem just like every other water heater installed; put it in and forget it.
This scenario causes the buildup inside the water heater that loses that once efficiency that everyone just looooooooves to number crunch thinking those numbers stay imperative after that first year...it doesn't.
When a water heater has to run longer cycles to accomplish temperature settings because of buildup, that's when mechanical failure begins.
The anode rod I promise is gone in that tank, unless you have what everyone doesn't have; good water.
If the water heater hasn't been drained once a year it is a inefficient water heater as it has to heat through a layer of sediment you won't remove from that tank at this point.
If you're broke then take your chances and replace the valve. You're still going to have a 8cyl car running on 6 leading to 4 or 3 the longer that water heater stays in operation as buildup in those tanks reduce the % of water containment and forces the unit to cost more money to operate.
So the lone rebel that has a water heater in his basement for 30 years thinking he has won the battle...is an idiot because technology advancement, burner AND thermostat designs have changed, and the required R value for insulating those water heaters are far greater and do a better job of slowing down, not stopping thermal loss.
The hard science is the majority of people operate their plumbing till it breaks, and rarely do they perform maintenance on their plumbing system to avoid creep-up issues.
But hey, I just got my plumbing license yesterday off a box of popcorn.
