National Guard to active duty after age 42?

You could potentially go back to the National Guard and then transition to the regular army. I was 36 when I transferred back to the regular army as an officer. They only took me back because they were in need of infantry officers. I will say that it is a young man's game. The Army looks for longevity. If they can attain their numbers through regular recruiting they don't necessarily reach out to take National Guard soldiers unless there is a need. You would have a very hard time transitioning back to the regular army at 45 unless you had a very unique skill set.

Talk to your recruiter. They will subtract your previous years in service.
You should also check into the Air Force reserves the age cut off limit right now is 39.

"• To enlist, you cannot be younger than 17 (18 for GED holders) or older than 39 years of age. You must begin Basic Military Training before your 40th birthday."
Source: https://www.airforce.com/frequently-asked-questions/physical,personal/what-is-the-cutoff-age-to-join-the-air-force

Which means you subtract your years in service - you said you did 4 prior - so that would make you 39. So you need to go NOW! Like TODAY 1/18/2021! Because Air Force has certain quotas but going Reserves will probably be your best bet. Going active will be another story but at least get your foot in first.

You just said you're too old to go active duty, how would you be able to go active 3 years later?