According to the GC2410 manual, it requires a yearly coolant flush and change. That seems a bit excessive, but I'll probably go ahead and do it this fall/winter to be on the safe side.
Lots of vehicles these days recommend the same; even brake & tranny fluid! Not like the old days, I guess, but I think it's not a bad idea if you plan to keep your rigs for a long time! But once a year? Maybe every 2-3?