There are a lot of 285, 320 and 345 guys on another site that all did the steel gear swap last year. I did mine 2 years ago and was always hearing it was prone to happen at around 1,000 hours. I know the lower HP Kawasaki liquid cooled lawn tractors like the LX178 and LX188 it was pretty much unheard of for them to fail but the higher HP 285, 320 and 345 garden tractors had a much higher risk for failure. I have always heard it was a matter of when... not a matter of if.
Many people are intimidated by this but its not as big of a deal as many think it is. If you can pull the motor out and let a mechanic shop do the steel cam gear swap its not too expensive to do. It is worth doing it before it fails because when it fails plastic pieces will be everywhere inside the motor and the pistons can hit the valves bending the push rods and possibly the valves too.