Your experience is obviously different but since I have been on the supply side for 10 years now 4 as an employee and 6 as an owner I think I've seen way more machines as a whole to base my opinion on is all I'm saying

now you might be having the issues on your machines and those in your area because of other issues human or environment
.As for the warranty yes belts at covered unet
Prochem's 2 year warranty. We have only done belts twice under warranty and those where a problem with the manufacturer which Prochem has since changed quite a long time ago as Vince experienced.
As to the issue your friend is having there isn't enough info for me to base an opinion on but I have no problems with warranties with Prochem. Is it Prochem or your distributor that he is having issues with? I can tell you the engine and blower and pump all are their own individual warranties from each manufacturer which is the same with every manufacturer, SS, hydra master, masterblend a d even Judson.
Those can be a huge pain if you have to deal with one of those but usually Prochem takes care of most of it unless it has to go in to a authorized warranties center like Koehler demands which not all distributors are authorized Kohler warranty centers. Your welcome to have him contact me and I can see what I can so to help him.