The only driveshaft splines i've ever seen worn out are on the K75 and K100 models. The pre-paralever models from 1984 to 1989ish.
Clutch splines can wear on all models, but it's a job and a half to grease those.
The clutch/gearbox splines are fine on 98% of the bikes i do a clutch change on.
The other 2% are having a clutch change because the splines have worn out
On pre 2009 1200 models you have to swing the final drive from the shaft to change the final drive oil, so you can lube them on a regular basis anyway, you don't have to make it a specific job.
Unless you let any old bike workshop who don't specialise in BMW's service your bikes, as they won't have a clue what to look out for on BMW models.
The shaft U/J's seem to fail on 1200 more so than the 1100/1150 models. .