Very interesting but practical question.
Ideal gap between boy and girl should be 3-4 years.
Your sexual life will be dependent to
testosterone level and your habits, lifestyle and other stress factor.
You are going to marry a girl not any week that you are keeping one day holiday like Sunday for her :-)..
Good relationship requires time, trust and care.
Keep these 3 in harmony for a good marriage life.
I would suggest some test to you as you are planning for late marriage.