Slick mags when mine are good?

A mechanic that worked on my aircraft tried to push me to buy slick magnitos
and when he was done repairing my airplane he said "Ok the noise you brought
it in for is gone" It was, and the plane ran like any of the planes he works
on for a local flight school. Not wonderful, and surely not as good as when I
brought it to him, but it ran ok.
I went in to talk to him about my now rougher running engine to hear from him
exactly what I expected "You have the older style magnitos and you need new
slick mags."

To make a very long story short, I got stuck at another airport when I had a
bad mag check during run up, the next mechanic to work on the aircraft said
it was timed wrong, and there were a few other issues. It runs perfect now,
thankfully.

When I returned to he first mechanic to question him he said "I told you that
you would have problems with the old Bendix magnitos." Of course I dont think
anyone in their right mind would fly an aircraft knowing there would be
problems with it. He also put "Ignition system is good" in my engine log book.

Is this true that the old style magnitos should be replaced or is something
wrong with this whole thing? If the old style Bendix mags were something that
needed to be replaced, would the 40 aircraft and mine have an AD on it? I
just bought this aircraft, a 68 Piper 140, and have little experience with
engine repair, but this seems very fishey.

Thank you for your time
Steven Aulisio
239 Hanson Dr.
Springfield MA