Zero Turn Mowers

I have a Husqvarna LZ5227XP commercial mower that I bought new in 2006. I mowed with it a year and the hydraulic pumps went out. They were replaced. Mowed with it a year the hydraulic pumps went out. They were replaced. I mowed with it almost a 1/2 season with it the hydraulic pumps went out. The dealer talked to a Husqvarna Tech which instructed the dealer to replaced the hydraulic pumps with ones that have cooling fans and to remove my hydraulic cooler. That ordeal took almost an entire season so the mower sat for one year. Well those pumps have gone out in the middle of this season even after the dealer instructed me to install a cooler in the hydraulic system.The mower has almost 800 hrs. is that the normal for a Husqvarna commercial mower. All work and repairs or maintenace have been done by the dealer. The pumps seem to last 1 1/2 year before having to be replaced. What is the deal?