I am in the 'high school sweetheart boat' as you put it nutz.
I first met my GF when I was 10 years old. Got together when we were 17 and its been happening ever since.
I'll marry her one day but I don't know when. We don't need the contract to prove anything.
I don't think the whole pissing it up until your 30 would sit with me personally. Your starting to wonder too by the sounds of it (considering you bring up such a personal topic of a footy website).
If your going to spend the rest of your life with someone and they mean so much to you that marriage is involved, wouldn't you want that 10 years of pissing up to be used spending time with the 'one' while you can.
You never know when things will come to an end. To me, my girl is more important than drinking or footie and thats why I would never ever in my life consider what could have been if I had just partied that little bit longer.
However if you do happen to find missus right this weekend, just make sure her name isn't 'always'