First thing I check on a water heater is the age. Newer ones have a build date on them. Older units the date is in the serial number. Google your brand of water heaters age. Most likely will take you to the building center and that will have instructions on how to read the date. All other dates on the water heater have nothing to do with the build date.
Next I’ll open the outer door to the burner. If there is water in there it’s more than likely a leaker.
If you got 12 to 14 years out of the water heater that’s a good run. If it’s over 20 just replace it if it’s leaking or not.
If you are located in the north metro let me know if you need any help with a new water heater. I install a lot of them.