God wasn't surprised this guy was healed after he turned 40. The man was born with disabilities -- he never could walk. God could have healed him earlier but He had a reason to wait. The fruit of this healing was quite amazing.
"But many of those who had heard the message believed; and the number of the men came to be about five thousand." Acts 4:4
God is so good to redeem our entire lives when we give them to Him -- even the part of our lives that wasn't lived for Him, our pasts that, prior to Him, seemed desolate. When we give our lives to Him He will give new meaning to our entire life: past, present and future.
I am guessing that when this man was healed and saved, God gave Him back many more blessings than the pain of His past.
This gives me great hope. My 12 year old son has never walked, never talked, never used his hands for fine details or even sat up on his own. I am filled with hope and expectation about the day he is healed and then the future that will come after his healing. God will surely give back to him what he has lost. One day!