I don't think its the length of time people have to wait that is the problem, its the transparency or rather lack of it in the whole process.
If my car was due to be changed in 6 months, I'd walk into the garage tomorrow and order and happily wait the 6 months if that is how long "they say it will take".
But to be told 12 -16 weeks then add another 10 on is just a nonsense.