Are wireless transceivers affected (performance or life) by strong magnetic fields? If yes, why?
It depends on a few things...
Is the magnetic field static or changing, and if changing, how fast? A quickly changing magnetic field is pretty much a basic radio transmitter in itself, so will probably affect nearby radios in the form of interference, which is an effect on performance but not life. A static magnetic field (for instance, setting a permanent magnet on the side of the radio) will probably not do much of anything, unless the magnet is extremely strong (don't put your rig in an MRI machine or particle accelerator) or the magnet happens to be very close to an inductor or transformer, and even then it may not be strong enough to do much and the negative effects should go away when the magnet does.
The only risk of permanent damage I can think of is to moving parts, especially sensitive ones like meters, that might get bent by too strong of a magnet and no longer align properly. And even a weak magnet near a meter will cause it to malfunction or stop working entirely as long as the magnet is nearby.