It is almost always better to spend miles first and then worry about buying flights later. There are obvious exceptions, such as 25,000 miles vs. a $50 fare, but in general "earn and burn" is a phrase that exists simply because it really is the way to go... And unless you have a really safe and secure job, saving $$$ is never a bad idea. Yes we expect to travel again, but you never know what life will throw at you. (such as a pandemic)

Don't worry too much about devaluation. Airlines can only get away with that when the going is good. When travel gets going, there will be a lot more empty seats available as saver awards. Airlines won't really want to leave airplanes parked in the desert for long... if they can cover their fuel costs for flying it...