Even when I only had a couple snakes I was raising my own food...and I really don't have all that many compared to some here now. Raising your own rodents can be a very fun aspect to the reptile hobby. Many people will tell you its not worth it and often have some sort of rule of thumb however everyone's situation is different. You are on the right track in your mention of controlled breeding. With just two snakes controlled breeding will be important unless you have a way to freeze or sell off the extra mice. I word of caution mice can get stinky! Raising rats is another option and you can feed when the offspring is of appropriate size but if your snakes are pretty small yet stick with what you know they are feeding on.