From the Wiki FAQ : The basic gist is: we'll fairly compensate you for the remaining time on your current subscription, you won't lose out on any money by upgrading part-way through your current subscription. Here's the nitty-gritty details. All upgrades are pro-rated. For example, if you upgrade from a Plus, Monthly account to a Pro, Monthly account, and it's half-way through your monthly subscription period, you would receive a credit for 50% of the cost of the Plus, Monthly subscription, which is applied toward your new Pro, Monthly subscription. Note: You WILL NOT be charged immediately when upgrading your subscription, instead you will be charged on your normal renewal date for the small amount of time that was left in the month, plus the normal monthly rate. As for the Pro sets, there is a wide variety of styles, and a good number of basic monsters are covered. You might consider upgrading for one month and judge for yourself.