I did my initial issue Class 1 medical and FI course aged 57 and have been instructing for the past 10 years (you needed Class 1 in those days for FI, not now, though). I'd done the CPL exams in 1990 and had an unrestricted BCPL issued against a Class 2 medical, hence the initial issue at 57. I had around 500 hours, all SEP, when I started the FI course, all paid for by myself, having never progressed to a commercial job. I had a great career elsewhere in the aviation industry, which packed me up when I was 57.
It is undeniably harder and takes longer to learn new things when you're older, but I believe that maturity brings other things to the table.
Go for it!
TOO