I've replaced mine every 12 months give my mum one and my brother the other and both still working great.. It's the filters that may cost this vac a shorter life span by burning the motors out, the filters work ok about 6 cleans then become less breathable you can visibly see this when the filters start crushing in because airs not passing throu correctly. I clean the filters like mad too, give up with them now and things seem better with my own make shift joby.
Hope this helps you a bit.