Can I upgrade for just a month?

This time of year around the holidays we use way more submissions than normal. Can we upgrade our usage for one or two months, or would we be required to upgrade for a whole year? 

You can indeed upgrade for a single month.  We have many users that need extra submissions for one or two months a year during peak season.  Upgrade during the time you need to higher limits then cancel the subscription when you do not.  As long as you stay under the Free account limits after cancelling the subscription, your forms will continue to function as normal.