Assigning hours of operation to the life of a clutch is ridiculous. it depends on how the tractor is used. When I purchased my USED DK55 with 2600 hours, the clutch was slipping. The tractor came from a landscape supply yard. The three point hitch and the PTO were never used. It was used strictly as a loader tractor. 2500 hours is a lot on a clutch constantly slipping. That is why industrial tractors use torque converters instead of clutches. Those of you who comment on having high hours on the tractor are not using it as a loader tractor, it is a tractor with the occasional use of a loader. As for throttle down, unless you are using a very high gear, most tractor activities do not require riding a clutch regardless of engine speed. Back blade or box blade work is performed at 1 MPH so the clutch is on off.
Try the adjustment. The factory builds in room for adjustment. That is free. others who profess that as long as you are ready to spend thousands are only saying so because it is not their money.