You're right man, it's hard to believe that you're having sex since you were 8 years old. Rare, I'll say. So, the only question you've asked is if sperms become dead if masturbation is a one's habit. No, sperm are produced untill you're dead or untill you've sufferd an serious accident causing damage to your head or testes. You'll surly become father. Excess masturbation may lead to less volume of semen but that is only temporary. Thevolume is restored if you give some space.
But remeber, excess masturbation is not good. No, ofcourse not, it makes you infertile but there are some other harms. For instance, loss of more energy, divertion from work etc. So, if you're able to get rid of masturbation as a habit, it will be better. And, enjoying sex even 90 times a year is no harm and will not reduce your sperms.