A properly designed and manufactured final shaft drive can be nearly maintenance free. Cars and trucks have been using shaft drive for over 100 years, and most manufacturer’s designs are nearly bulletproof. The reason used 40 year old Honda cx500 final drives are so cheap on eBay is because nobody ever needs a replacement, they last nearly forever.
BMW shaft final drives were fairly reliable (except for wheel spline wear) until they came out with the double jointed paralever system. The paralever has handling advantages but has also had reliability issues directly related to the design. There were also manufacturing issues with K75 final drives that caused many repeated failures.
Given the choice, I’ll take shaft drive any day, car or bike. The trick is getting one that is both well designed and manufactured.