3rd year on the 9550 here, got it at 1100 hr.   Traded a 9400 with 15 yrs use.   9550 has a lot of plusses, some enhancements to cab and controls, more power.   The 9550 will eat crop faster than an earlier machine in its class, more grain going through equals more wear on a per hour equivalent.   That may be old news to some folks but we are doing a fair amount of fixing on things which I thought should be good until 2000 hours, the previous owners kept the machine busy.  The 9550 with 1500 hrs you are looking at might need a good inspection and some questions asked to see what has been done to it.