i can tell you the cheap generic ones last about 5 years with alot of use, then the sensor and heating elements can get unreliable, also the cases can warp with time which changes how they seal and ventilation characteristics .. fans can need replacing before then, but theyre pretty standard and cheap to replace ..
But I did vote "4-5 years" since that seems to be the average number of years my hens have continued to go broody. I find that interesting because it's also the current leading number of years in your poll.
), fourth was finishing up some eggs that my hen abandoned. It was only on for a couple days for the last one. Third incubation had some issues where the bator shut off several times, on top of losing power for about a half hour, but that could have been due to my unfortunate overstuffing. It doesn't have a thermometer or a hydrometer, but it's done a great job so far.
This year, I was so sure I'd have plenty of broodies to help me hatch eggs because I have three hens that generally all go broody together late spring to early summer and never quit until they go into molt in late summer to early fall, but this year, of course, they all decided they didn't even want to brood! 
