Whenever you've discovered God (the infinitely huge ball of white light) and your partner has too, and you've both seen to it (or known) that you are both 100% saved, or will be. That is the time to get into a relationship that hopefully you will stay in forever. Age does not matter. But aside from that... I was 20 and my boyfriend 30 when we met and almost immediately fell in love and started a long term relationship, and he got me pregnant. Now he's 32 and I'm 21 and a lot of s**t happens between us and there are differences (and unfortunate similarities, where we seem to be too much alike), but we will always have that common denominator at least.