Would only continue acquiring DL miles under two scenarios:

1) You are a DL FF (like me) so you generate SkyPesos at a reasonably fast rate and don't hold on to them for too long given their frequent devaluations

2) You do an app-o-rama and take advantage of all the new AMEX offers (would want it to be at least 60k or 70k for Gold/Plat cards) and then spend without holding on for too long

Otherwise flexible currencies are your best friend these days.