Hovabators for the long run?

I just noticed a thread in which several people commented that styrofoam incubators work well the first year but that hatch rates drop significantly in future years, theoretically due to bacterial contamination.

So, my question is, who has had their styrofoam incubators for more than a few years and found that they do or don't hold up?

I ask this because I bought two Hova 1588's this year, and had pretty good luck with them, but don't know what to expect from them.

I do know that I need to thoroughly sterilize them, but I'm just curious what results you more experienced hatchers have had with them over multiple years' use.

Thanks.

Susan