Its never too late to stop having sex. Would it matter if it were another sin? Stopping sin is stopping sin, no matter what the sin.
Also, 'reborn virgins/born again virgin' is not a biblical idea. You aren't virgins anymore, period. But that doesn't mean to keep having sex, as the bible speaks plainly against sex before marriage. It doesn't say 'unless you had sex before', it says 'don't do it'.