Yes, failed alternators, mags and vacuum pumps are a bummer.
Here's how I think about it, what I've done and plan to do to minimize the bummer part:
- I have dual alternators (and batteries) either of which can run the essentials through a full tank of fuel. If one fails, I'll probably wait to get home to replace it.
- I have dual mags. The plane runs fine on one though I will have it swapped out at the next landing if it fails. I personally inspect and maintain my mags but also have started performing the inflight ignition system checks to help detect problems before failure.
- I have eliminated the vac pump and have an all electric plane, see dual alt/batt/bus above
I don't intend to retire any of these items until I detect a problem that is best addressed with a new or overhauled replacement.
One of the ideas that Mike pushes is that component failure is not necessarily a catastrophe. Dual mags where only one is needed for satisfactory engine operation. Dual alternators where only one is needed for completion of any flight. Single vacuum pumps for IFR work need a backup no matter how they are maintained so that you get it on the ground safely.