We'll start from the beginning. By the time you are in primary school, she would already be in primary four-which, technically is upper primary and while you're still frolicking around with pokemon cards and going ewwww at the prospect of holding hands with a girl while walking to the canteen, she's already reading sweet valley high and thinking of kissing. Perhaps more, but you get the drift.
By the time you enter secondary school, she would already be graduating that year; ala senior with some dork who is still trying to figure out his environment and a "himself" that he would ditch when he eventually matures. By the time you enter JC, she would have already completed it. And while you are slogging through National Service, you fall two years behind in terms of advancement on the corporate ladder. That brings you to a grand total of being half a decade behind.
The World Cup, Olympics and General Elections are held once every four years. Surely that indicates how drastically things changes across a four year period. Need I mention five?
Look, I'm not saying not to go for someone older. In fact, I think that doubles the fun. Just cap it at two. Anything more is just heading for a colossal mindfuck. Besides, I don't think you want a mother for a wife, do you?
Shoot, score, smile.