Went back to Ohio with two of my sons last weekend for the Nebraska game. Purchased them via Ticketmaster (OSU's ticket partner) as we were walking out the door to the stadium. A week or two in advance and they were double/triple what we paid four hours before kickoff. I've done the same for bigger games as well, basketball games, games in different cities, etc. When I've needed more than four (six for the Michigan game, a dozen for the national championship, six for NCAA tournament, etc.), I usually have to buy in advance as those quantities are harder to find and don't last long.

For BYU games when I've needed a couple, I've always bought outside the stadium (even when I was a student I'd buy better tickets than my student tickets). But again, a bigger group would be different.