I think that there are no direct answers for this. I would like to know the age of the Apostle St Paul when he encountered Jesus on the road to Damascus and how long he lived after that.
It is somewhat impossible to know for sure how old St Paul was at the time of his conversion and death.
The Apostle Paul according to Wikipedia was born between the years of 5 BC and 5 AD. Most websites place his birth between the years 3-5 AD.
As for the Apostle's conversion, it seems to have occurred between the years 33-36 AD. Most websites favor the year 33 AD.
And finally, St Paul died as a martyr between the years 62-67 AD.
Thus St Paul was around 30 years of age at the moment of his conversion and 60 years of age at his death.
Paul never mentions his age in the Bible; however, what is known is this: He was a 'young man' when he persecuted Jesus [see Acts 7:58], right up to the point of his conversion in 36 C.E. By Jewish standards of the time, as according to the Mishna, a young man is one who is 30 or older, so at the time of his conversion . . . [Paul could] have been anywhere between six years younger or 24 years older than Jesus.
However, he also mentions in his letters that in 55 C.E. he was an “old man” [Philemon 1:9; see also, for example, Romans 16:23; 2 Timothy 4:6-8; and 1 Corinthians 4:15 for hints about Paul's age] and by those day’s standards an old man was 60 or older. In addition to some other scholarly speculation . . . his birth date is probably unknowable, but . . . [some scholars assume] he was born probably around 5 C.E., making him slightly younger than Jesus.
Tradition has it that Paul died in Rome as a martyr. With the above information as a basis of calculation, the year of his death could perhaps be between A.D. 62 and A.D. 67. (For further helpful information, see this chart).