The Bell System did not want to have to repair anything, it looked bad in the customer's eyes! (Of course a lot of other stuff besides phones was built better 40 years ago!) 1A2 systems went in with the legitimate expectation that 25 years was a minimum wear out point. The weakest part was the interrupter. Motor driven cam that operated contacts for ringing line lamp flash, on-hold line lamp flash, and audible (ringing). The weak part is the motor, but they normally lasted at least 10 years! No contact ever carried the current they were capable of, relays are 'underloaded', there is just enough stress in the equipment to keep it working! The 5 line phones would bust your foot if they fell on it, but they would STILL work! You could drive nails with them, except they were awfully heavy, (5 pounds) and very awkward to swing!
Ahhh, the good old days.
