Air traffic controllers require a significant investment by the federal government, I take no issue with age limits for both investment (lower bound) and safety reasons (upper bound) (if the data says it is reasonable, I'll always defer to the data).

I take exceptional issue with the fact that their pay is not considered essential. There should be no way for this critical infrastructure to be not considered essential. ATC pay should flow regardless of actions of any branch of the federal government, and there should be robust systems in place to ensure these workers are not pushed beyond reasonable work limits. Fix the system or break the system forcing a fix. If it continues to work "good enough" without a fix, no changes will be made.