MuMetal Experience

[stephenl]

I've seen mentioned several times to be careful not to "over work" MuMetal. How much can you do without affecting its mojo?

[Orson Maxwell]

The permeability usually suffers greatly from compression and from cold-hardening that occurs during stamping and most likely during bending. Most manufacturers employ annealing after stamping which cursory increases the permeability for 20-30% (250-300% for some alloys). However such an annealing process is not easily done DIY because it requires high temperatures for prolonged times in inert gas environments.
How much all this will affect your project depends on what you are going to do with the metal, but the general "do not over-work" suggestion rings true.