A couple of weeks ago I was in rehearsal when one broke on my 1st valve. Luckily I was able to take one off my 5th to finish the rehearsal. Sods law I kept the originals in a tin that I carried with the tuba, but I changed gig bags and didn't put them in for that rehearsal!
Anyway, I've noticed the new ones seem to crack on the threaded shoulder so I've come up with a mod to strengthen them.
I got some 5mm ID brass tube and slid it over the threaded shoulder. It seems to work very well and is a nice tight fit. I did have to chamfer the ends to get them on.
Just an idea if you got cracked shoulders or to prevent cracking in the first place.
Wilf.