How do you bed them in then?
Go out on to the road (or somewhere equally clean & dry) and ride up and down like an idiot for ten minutes, banging on your brakes hard until they start to have a bit of 'feel' rather than the dead sensation of a new pair. The idea is that you are generating a bit of heat through them to harden (but not glaze) the braking surface. Another tip i've heard is to take a water bottle out and give them a dowsing down to cool them quicker after you've got some heat in them.
If you go out anywhere mucky without bedding them in, they'll crumble like Stilton in minutes.
Ooh, Stilton, now there's a thought…… 😀