Yes.Aren't two engines twice the problem and twice the expense?
However, statistically one of two engines failing is twice as likely as one.
I agree with what you are saying.Is that really true?
I've seem some anecdotal data suggesting that some twin-engine owners (of both boats and aircraft) may have the feeling that--because they have two engines--each engine may not need to be maintained to quite the same level a single-engine would be. Or to put it another way, a SE owner might be a bit more obsessive maintaining their sole power source.
Again, this is just anecdotal but jives with some things I've seen.
TwistedTree - How one chooses to address the three choices you cite is in part determined by the the likelihood of a problem occurring.