To answer the question posed above, donations ebb and flow. Over time, we meet our goals, but sometimes we don't. When we go over in a month, it averages out the times we don't make the goal.
Here's how it works: money donated goes through the OCnet Treasury application to a paypal account that is under my control and is recorded in the private Administration dashboard area of OCnet for tracking purposes. I pay the bills for OCnet out of my personal funds, and then reimburse myself from this paypal account. Besides their being able to see the Treasury application totals in the Admin section, I maintain a basic accounting spreadsheet that is available to the other administrators for purposes of open, full disclosure, and transparency.
When we get more than we need, which has happened a few times, I pre-pay the server costs in advance even further, because we get a discount by doing that. Eventually, within 1-2 years, we are also going to need more server space, since the forum database is getting huge. So that factors into my planning purposes as well.
The most money we ever stockpiled at one time was about $700, at which point I prepaid the server for two years. It is good through sometime in 2014 currently. Moneys collected now will be used to renew the server after that point, and toward the upcoming server expansion (which might increase our cost by something like 25-35%, but don't quote me on that, as I don't have the numbers in front of me).
If we ever got a really big windfall, I might also consult with the other administrators and moderators about ways to expand the site beyond its current reach; I had always wanted to make OCnet more than "just" a forum (although never compromising/jeopardizing this primary mission, since we do it so well), but time constraints and resource constraints have prevented that heretofore.