You're probably right. On my old ST1100 I changed the bevel gear oil once in 140k miles. But it wasn't a single sided affair.Never changed the oil in the rear diff of any car I have ever owned either, 1 with 650,000 miles on it. Car diffs have far greater loadings on them. Oil change requirements only came about because BMW got something wrong in manugfacture or assembly process and it became an ass covering process.
I'm had the paranoia bug installed into me. So I change it once a year as I tend to do the same miles each year.
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