Glueing drivers.

My first post here! Hello...

I have always had a pair of Polks in my possession since since probably about '86. I have been aware of the brand since dad bought a pair of (going by memory, I was probably about 11, which makes that about 1982) 10A. The 10A are long gone, but the Polks I currently own are...

SDA-2 (blade/blade, SL2000). My dad bought them new in '86ish
M10B (beveled front, SL2000)
M4 (Zelda tweeter, see, I have lurked here a bit! LOL) I LOVE these!

I also had a pair of "Monitor" which was the precursor to the S4. I gave them to a friend.

Anyway, my question is, is there a year or date when you don't have to worry about glueing the magnets on the drivers, or are all of the coated sticky drivers susceptible to magnet shift?