Bryan,
That sounds like the ave for a lower end rebuild for that service useage. The IHC T444E is also supposed to go about that many miles etc in the same useage.
Not sure I have truly worn out a motor per say, but have had to replace a few in the mid 100K mile range. most I would say were something more in the line of a major bang vs just wearing out. Altho my IDI7.3 at 140K miles is acting like it is worn out. Then again IHC called them a 100K throw away motor! You had to go to the I6 to get motors that would last in the 400K-1M mile range. or some of the more recent V8 designs after and including the T444E.
marty