To keep or not to keep worn parts

Phil FSI

My FSI is having a new alternator fitted today.
Battery light came on last week followed by various terrifying symbols and BLEEPS coming from the DIS regarding brakes and steering, by the time I got home I could barely move the steering. Was driving in the old days really that hard work ?
Anyway, my question.
Should we be keeping old parts taken off by the garage?
What happens to them if we don’t, Will my old alternator be fixed or melted?
It does appear they got a new one without too much fuss but are these old parts reparable, especially as our fleet get older and parts become scarce.

The alternators are used across a lot of the vag range so supply won't be an issue for a number of years. I've always got a couple on the shelf too.
Rectifier or brushes are common replacement parts. Often you can also get new bearings. The over run clutches are available. So yes always useful either as a source of parts, as a rebuild yourself or part exchange against a remanufactured unit.
The garage will need the old unit to return to the factors they use most likely. Yes they can be repaired but good second hand refurbished units I find is the most cost effective solution