Perhaps not the best forum, but I couldn't find a better one..

 

I remember from my younger days that there were some things you weren't supposed to do with magnets, including heating and jarring them. The explanation at the time satisfied me.

 

One thing I've wondered about off and on ever since, though:

 

Is placing (and keeping) two opposed magnets (N-N or S-S) in proximity detrimental to their long-term magnetism?

 

TIA..

if you are holding them together (applying a force) then yes, you will change the magnetic moments of the magnets domains reducing their magnetisation.

The effect is negligable for modern permanent magnetic materials (such as NIB). For older materials it is a serious concern. Alnico as an example, iirc.