Great question, I was just about to edit my question with these points !
Yes, 1974 4/4 - there's nothing particularly wrong with them. - apart from the age (as I'm over the age of 47 I shouldn't use that as a prime motivator)
The tend to lock very easily, so makes it a pain to extend, multiple tugs and the lap extender seems to be locked in place so I have to take a deep breath before fastening the belt - fine for driving up and down my street, but not for much further than that.
The fabric is fine and they appear to unfasten easily - my biggest concern (but I do carry a knife with me every time I venture out, just in case)
if there are maintenance tips, lubrication and W-40 etc , I'd be willing to apply these as a first resort.
