Never had to replace a starter motor, but I did have a one way clutch failure at 25k miles on the SEEG. Failure of the actual Nippondenso starter motor is very rare (it's not a Harley part, it's used on lots of automotive applications also), but for whatever reason the one way clutches do fail fairly often in Harleys. If you do an online search for Harley starter drives, you will find tons of listings from folks selling everything from the standard part to the supposedly lifetime guaranteed stuff. btw, some of those lifetime guaranteed parts are no different than the regular ones; you pay enough for the first one that they still come out ahead if they have to send you another one free.
I suspect that the issue on Harley's is related to the comment by LarryB. The shock loading on the starter drive when used in the Harley system is more severe than what it would see in the typical automotive engine, and if the compensator is weak it will allow more shock to transfer to the starter drive. Case in point, all the starter drive failures on the earlier 110's due to the cheesy compensator design introduced in 2007.
If you're looking for a new one way clutch, you don't need to pay Harley over $100 for their kit which includes stuff you don't need. Go online and pick up just the clutch for around $40.
Jerry