Marathon Man,

I do the same thing for my friends and family, namely my in-laws, who always travel premium cabins on BA, VS, EK or KQ, but historically never collected or redeemed miles.

Since I got married last summer, I have been able to use my in-laws miles for my wife (their daughter) for BA J from LHR-NBO return, and VS UC from LHR-NRT return.

Oh, and I also got an EK Y award from LHR-DXB-NBO return for my brother in-law, which made my in-laws very happy.

Finally, I have a lot of friends who have been flying VS to Nairobi, and have been referring all of them from my / my wife's / my parents' / my in-law's accounts, accumulating thousands of miles in referrals. Many of these people may never fly VS again, or even collect miles, but I have gotten tons of referral miles out of it.

Anyway, I do it all because I enjoy it, and like the OP, don't like to see miles go to waste. Ah, if only VS had a household account...