That's all fine and dandy for people who think like that-- but personally I recommend doing magic every day.
Yes, that's right. Every day.
Why? Well, there are two main reasons that kind of say it all for me.
First of all, and probably most importantly: practice makes perfect. Magic is a learned skill. You don't become adept at magic by practicing it every 4 or 6 months. You become adept by practicing it often. Even if you practiced it often for a while, then stop for a while, it can take a little bit of time to get back into your groove (not nearly as much time as it took to learn in the first place, but still-- yes, you can get a bit rusty). Just like with an artist, or singer, or musician, etc. who needs to keep up the practice, you gotta keep those skills honed.
When those desperate moments come, don't you want to be on top of your game? How do you think you get there? You practice with the small stuff.
Second, don't you think it's a bit ridiculous to wait to help yourself until you're in a desperate situation? Would you wait until you're starving to death before you get up to plan a meal? Would you wait until you're on the brink of homelessness before you started working to earn the money to pay rent? Are you going to wait until you're dying of cancer before you seek treatment? Of course not... being pro-active is not just common sense, but it's the way you improve the quality of life.
How is it noble to wait for things to be out of control before you use your talents and resources to help you? Isn't it more noble for you to prevent you or those around you from reaching the point of suffering?
Tips for Living Wicca: Practice magic every day.
Mind you, that's practice magic. That doesn't mean you need to practice ritual or spell craft every day... simple positive affirmations to attract that which you desire, putting healing or calming energies into your tea before you drink it, send that tired friend a jolt of energy in visualization, etc,-- these are small ways to incorporate magic into your daily life for little things. By taking care of these little things, you hone your skills and you keep ahead of the game (think of it like preventative medicine).
Magic is not like fossil fuels. There's not a limited amount that will run out one day and be the end of it. It's not a wasted resource... it's part of nature, it's in and around us at all times. You won't use it up, you won't cheapen or disrespect it by using it. It's not greedy to use the resources at your disposal responsibly, just like it's not greedy to stock the pantry or plant your crops or put gas into your car on pay day. You have the means to keep things running smoothly and make life what you want it to be. Use it.
How often do you use magic?