Poor backup

Just replaced my second Heat tech over counter water heater in 5 years. Ariston refused to honour the warranty on the grounds that I didn't service the geyser as required. I never knew anything about servicing it, and neither did Build-It, the supplier of the unit. Clearly, if I'd known I would have taken steps to do it. I've now replaced it with a Kwikot 10ltr over counter geyser, which the plumber tells me will give me no hassles. Interesting too, although Kwikot do recommend a service every 2 years (bad water area), no mention is made of its effect on the warranty. Poor show, Heat tech Ariston - no referrals from me, ever!