Merahl is nearly 50, having initially tested when being a capsuleer was risky, deciding against it, having a career and a family, and then cloning was introduced, making the idea more acceptable. As far as aging in Eve is concerned, I see him as being not quite middle-aged.
Consider that with today's technology more people are living into their 100s, and that most of us born in the latter third of last century can likely expect to live well past that. Having an unaugmented person in Eve, provided they had access to good medical facilities and a healthy lifestyle from infancy, live to 150 is not unfeasible. In terms of capsuleer qualifications, I think there would be more concern regarding an advanced adult's state of mind than over their physical age. People tend to be set solidly into their ways by the age of 50 or so.