I knew an engineer who gave up his high salary and house to attend college for 3 years taking pre med coursework..and then medical school..at 42 years of age. Which isn't that old when you think about it. His wife was supportive generally speaking but I suspect inwardly she was really grieving over the sale of the nice house.

Just depends on what you're prepared to give up and what you enjoy doing.. Special Forces probably would be a no-no to guys 35 and up, even with an age waiver..as most of the wives would $hit a brick over the thought of sleeping alone and wondering if their hubbies were being shot at overseas. Not saying they couldn't cut it physically..it would just be hard giving up everything they worked for thus far (divorce rates are high for special ops guys in the Navy I was told)
Jam it back in, in the dark.