Ha, who needs mechanics anyway!

[ribbert]

Mechanic bashing is a popular topic here. However a mechanic would never re use master or slave cylinder seals after removing them, unless the cylinder was reasonably new (in which case there would be no need) or they have SS liners.
He would do this for two reasons, he knows he shouldn't and why, and the times he did, it came back an bit him on the bum.
Caliper seals don't matter quite so much because they don't slide when used.

Seals 'mate' to the bore. A rear brake m/c might not matter so much but it's not a risk worth taking with front brakes.
Either leave it alone while it's working or if you want to clean it out, do so with it assembled.
Seals are cheap.

You might get away with it and if it's your own bike you might say it doesn't matter, but it's not something those shifty, slack, wouldn't know if their arse was on fire mechanics would do.

IMHO

Noel