I am almost 84 now, and I have masturbated almost every day from the time I knew that I could. I'm about twice a week now, but at your age it was usually twice a day. Hope this helps.
Nope, you shouldn't be concerned at all.
In fact, there are several studies now that show that regular ejaculation can help prevent prostate cancer.
The only concern about masturbation is if you do it so much that it interferes with your daily activities like your job, seeing friends/family, affects relationships, etc., or causes physical issues like chafing.
Otherwise, no worries at all.