Sure, tier 5 will cover the entire Delta schedule while 1-4 will only cover flying on Thanksgiving and Christmas day w/ a mandatory layover in ATL. It'll just cost 500k to go ATL-MCO one way in Y. You can definitely use the miles easier b/c there's so many options...you just won't have any miles left.

Burning all your miles isn't hard...burning them in a way that you consider a value is a different story and actually reducing the # of miles it takes to go somewhere would cost them a lot of otherwise revenue generating capacity which is something they're not in the habit of doing.