You never know
A long long time ago, when I was about 15yrs old, took a flight (without parents) from LHR to Jersey, in a viscount. In the cruise I noticed a crack across the top of the LHS inside engine mount, slowly getting longer. I ask the CC if it was normal - they didn't know, but told the flight deck. Man with stripes arrived, looked at it and with horror in his eyes said "that's normal young man, but we will stop the engine to be on the safe side". Safe 3 engine landing was the result.