I have a KA that is 22 years old but still working (this is not a Hobart made one but is still MADE in the USA, not "Assembled in the USA", like some of the newer ones are marked). However, I noticed the motor was straining with a heavier dough. Due to the way it sounded, I'm sure it would have given up in time and I didn't want to ruin it.
I was very fortunate that my mom (who is 88 years old and who I care for on a daily basis) volunteered to buy me a new Hobart N50. This isn't an option for everyone (way too expensive)--I know I wouldn't have purchased it without some help--but if you can find a good used one, it might be something to think about.
Just be very careful if you find one on eBay. The first one I bought on eBay was disaster but eBay Buyer Protection took care of it as it was SIGNIFICANTLY misrepresented. I think the best thing to do is look for a seller that has a lot of good feedback. The seller I purchased this bad one from had all good feedback, but very little of it. The new one I ordered from Globe Equipment, a reputable restaurant supply. By the way, I highly recommend Globe Equipment to buy from, as these people are EXTREMELY helpful.
There are also Globe brand commercial 5 and 8 quart mixers (good sizes for the home) out there that are MUCH less expensive than the Hobart, but I just read on another forum that a buyer was so dissatisfied with it that he sent it back. He said it jumped around the counter with heavier dough and the motor heated up quickly. I can't find too much information on Globe but this was the second time I read that the motor got hot. To me, that is the first sign that it is apt to fail.