If the implied question is "Should I burn up all my miles now?", I don't think it is ever wise to build up a huge stock of miles in the expectation of working your way through them during 20 years of retirement. Even without going bust, airlines often change the Terms and Conditions of mileage schemes, making them more expensive to use or maybe even just deleting very old miles.

There is usually some advance notification to changes in Terms and Conditions (although not of bankruptcy!) but that isn't usually enough to burn through millions of miles.

Personally even at the best of times I wouldn't keep more miles stored than I earn in a couple of years, and in the current climate I'd be a little bit more cautious than usual. I ran my miles store down to 2,000 in December and I'm not keen on letting it get too much above the 100k mark where it is now (despite spending some recently) - but for those who earn millions a year, their limits would be rather different.