I have always washed my bras in washing machine and most of the time been fine, but recently 2 of my bras have had the wire come through, and one of them shreded some of the plastic rim inside the machine. Typically they are my nicest ones
I use a wee "delicates" bag. Had one that came with something else (washing tablets?) that worked for ages and then once it disintegated,I bought one (actaully, it came in a pack of two) from either Sainsbury's or Lakeland Plastic. It's a small mesh bag with a zip. Useful for bras, tights and children's socks.
Once something had languished for over a year at the bottom of my laundry basket , I realised that I should either wash it in the machine or not bother having it, since I was getting no benefit from it.
Lakeland do lovely delicates bags which are shaped and do wonders for my bras. Still got bra that's 3 years old and is pristine (doesn't have bobbly bits on it). Doesn't fit very well now, but that's another matter!
I always washed mine on handwash/wool cycle. However, after years of being advised by shop assistants that I should handwash them I now doing just that in an attempt to make them last longer and try and keep them in good shape. It doesn't actually take too long and not as much as a pain as I thought it would be!