How long do pool heaters last?

Well, the way it was explained to me, the heat exchanger is rusted out, the heater fan is shot and a couple of other things. Like I said, I have no experience with pools or their heaters so I appreciate any input.

The unit is a:

Teledyne Laars LX
Mod. LX400P
Ser. A99L10250
Propane gas
78% efficient

Does the “99” in the serial number mean it is a 1999 model?

Thanks.