Set the start time of giveaways every 15 mins, not instant

Yeah, but I don't know if that's a great deal, and definitely don't really know enough about the subject, that's just an opinion. xD

I totally find the idea useful should the server load increase anymore, but not right now!

When you fill out the create giveaway form you're basically just creating a row in a spreadsheet. Sites with dynamic content are almost always driven by databases and store very little static content that's sent to the user as-is (basically only for caching what little static content there is, or cheating a little by doing things like storing the number of entries and adding/subtracting so you don't have to count the number of entries each time someone loads a giveaway page).

On loading a page the server looks up that row on the table (and any necessary related rows from other tables) and populates the page template for you before spitting it back. To the web browser it looks the same as any 'ol static .htm page, but there is no page, it's all in a database.

There's still no comparing the relatively small number of giveaways created every 15 minutes to calculating points for over 100,000 SG users every 15 minutes (I don't know the exact numbers, but I know there's well in excess of 100,000 users registered).

Generating pages doesn't take much in the way of resources anyway -- it's just a template that gets filled in with info you provide for the GA and a randomly generated link is created (using whatever algorithm SG uses). Hundreds of people accessing those pages creates a lot more workload for the server than actually creating the page to begin with. Hell, I'd be willing to bet updating these forums constantly is a lot more workload than GA creation.

EDIT: you're not really removing any of the server workload with your suggestion -- you're just making the server do the exact same workload at timed intervals rather than spread out over that 15 mins.

You may be correct about that, but those points still have to be calculated and distributed to 1000's of users.