They don't have official "hour ratings" to my knowledge. At least I've never seen anything listed in any of Kubota's publications. Have seen tractors with 9000 hours plus. Have seen them completely demolished in 20 from negligent operators.
Most don't maintain them well enough and/or often enough and they still last a long time.
HST? Don't see very many failed. The old ZD mowers yes. Everything else not so much. #1 cause is overheating and #2 cause is lack of maintenance (run out of oil, no oil, wrong oil, water, etc). In close to 30 years messing with Kubota I've replaced 2 tractor HST's and I think 4 or 5 ZD 25 & ZD28 series mower HST's. Of the two tractors, one was a victim of an oil cooler bypass (ran a stick through the cooler, so consumer bypassed it with hose)-and that caused it to overheat and die a slow death and the other was a BX that had been missing the HST fan for many years; and was used VERY hard (as a bulldozer basically) on a daily basis. Most times the HST's outlast the engines for several reasons, usually maintenance related.
