Going through condensate pumps every 2-3 years
There is a big range in quality for condensate pumps.
 Condensate is actually hard on pumps and most of them are plastic, plastic seals impeller sometimes even bearing surfaces and case. 
The more expensive ones have rubber seals or ceramic and better level switches , many of the plastic ones I have found that are bad were because the shaft seals melted (plastic) I believe that the cause in part is because of contacts sticking or the pump running dry from mold when the pump runs dry melting the seal. 

The high end pumps I use in commercial systems cost much more but are metal,  both brass and stainless models with much better seals and capacitive sensors to turn the pump on. The price difference if you are going through them this often the more expensive is worth it because you only mess with it every 15-20 years and the seals are replaceable ~20$ and the sensors can also be replaced ~34$ this with a new set of bearings ~10$ for both and the pump is like new and will last another 15-20 years . so yes it can be the pump.
mold buildup can plug the inlet to the pump and run it dry causing failure quicker. I mentioned it but did not explain. Having some head pressure depending on where the check valve is if it has one can actually extend the life because there is water being pushed (as long the pump specs are not exceeded).