I'm looking at a used bottom bracket (Campy Athena) and used front derailleur (Campy Veloce or Mirage). Each is about 1/2 the cost of new.

Are those pretty safe things to get used?

Do BB's ever snap and make your cranks fall off and cause disasters?

From what I've read, older Campy BB's had a habit of coming loose. Did Athena BB's do that?