Should I replace a water heater preemptively?
The average life of a water heater is about ten years. Newer models are a lot more energy efficient as well. Given the age of your water heater, it has more than done it's duty. You don't have to replace it, but if it's in your budget I would recommend replacing it. You don't want to get in an emergency situation. I would also consider adding a concrete pad  or at the very least, a drain pan underneath your new one. That flooring situation is definitely not ideal.

Inspect your water heater:


Flush the water to remove any sediment.
Have a certified plumber take a look at the igniter and burner to make certain everything is safe.
Check for signs of rust around the bottom of the tank and at all of the fittings. If you spot rust around the water inlet or pressure relief valve on the heater, it’s likely that rust is also inside the tank. 


You can find out the exact age of your water heater by looking at the serial number on the  manufacturers sticker: