I'm 48, in the US, and had chicken pox as a child.

After my 43 y/o sister-in-law had a debilitating shingles outbreak last year I asked my PCP about the vaccine. He stated that he was wary to prescribe it to be. His reasoning was something like:

There was a previous shingles vaccine that didn't work very well. It was found that it didn't offer long-term protection and the protection could not be improved with a booster. The current vaccine is still new and the long-term protection and ability to be extended by a booster are unknown. Since most of the worst outcomes of shingles correlate to old age it makes sense to defer the vaccination hedging against the failure of the vaccine to provide long-term protection and to allow more time to elapse to learn more about how the vaccine works long-term.

Edit: My PCP's general advice was to defer the vaccination as long as possible. He felt that 60 was reasonable.

I haven't looked into the veracity of any of his reasoning, but I am willing defer to his expertise and bide my time. My sister-in-law had a really bad experience, and I remember my grandfather having a terrible experience when I was a child. I'm definitely fearful and would like to prevent it.