My opinion is go for it! When I was 28 I started in EMS, and many told me I was too old! But also keep in mind that the service I work for employee a 68 year old guy, who actually had a TI while patient loaded and driving. Some how he passed a DOT physical and was allowed back to work a week later. Just recently he "spaced out" and left a patient sitting in the hallway at the hospital.
I guess my point is, if you are wanting it, you are healthy enough to do it, then you should absolutly do it. But also be able to recognize your limits. Now I feel like a complete crap head for even saying that. Because the truth is all those things should apply and be in effect for everyone in the EMS profession, reguardless of their age.
I say do it! Good luck!