If you'd like some lengthier intervals between asking your parents to buy you more reeds, consider applying a few of these easy, time efficient methods on extending the life of your reeds!
Reed cane is like skin, it's got pores. And just like your skin, when the pores are open, they're absorbing all sorts of gunk. This gunk is going to keep your reed from vibrating efficiently, thus making you sound poopy. Try getting in the habit of brushing your teeth before practicing, especially if you've just had a meal. (If you have trouble motivating yourself to do this, try to visualize the contents of a cheeseburger in a blender being wiped on your reed and left to soak overnight.) By ridding your mouth of grossness beforehand, you've made it less possible for food particles and other nasties to get stuck in your open-pored reed. But if you'd like to go even further and fix the problem at the source...
...2. Get those pores closed to begin with!
This method works best on fresh reeds, so the next time you open up a new box, try this.
If you take a moment to feel the vamp of your new reed (the side that faces you when the reed is on the mouthpiece) you'll notice that it may be rough or scratchy. A reed with closed pores will feel smooth to the touch, so you want to start the process of making your reed smooth!
Take a rounded smooth object (I like to use the back end of a pen, but a spoon works also). Place the reed on a flat surface, preferably a smooth piece of glass. (You can use a window for this!)
Applying gentle but firm pressure, stroke upwards on the surface of the reed from center to almost tip. BEWARE: rubbing all the way to the tip may split it, so be careful!
The plastic cases that come with them are fine, but keep them all together in a tupperware container or a plastic bag that seals completely. You don't need a fancy reed case; what you DO need is a place to keep your reeds protected from the elements outside. Reed cane changes with the humidity in the air, and keeping them sealed when not in use will help keep them at the right moisture level for playing, especially if you've applied Method #2 and closed the pores!
4. Are you rotating them? (I'm pointing my finger at you and shaking my head judgmentally at this point)
Ever play on a reed for a long time in one sitting and notice it's got a chunky, almost green color around the tip? It's water-logged, baby! It's become so saturated that it's nearly impossible for it to vibrate efficiently. It's time to put it away for awhile to let it dry out. That means not playing it again that day, and not in rehearsal the day after either. You should ALWAYS have at least 4 reeds on rotation so that you are never playing the same one twice in a row. This is by far the easiest way to make your reeds last longer, so take it seriously! You'll save yourself headaches (and money!) in the long run!
Clarinet is supposed to be fun, so don't obsess. :-)
Rather than trying all these things at once; pick whichever one of these methods is convenient for you right now. You'll develop good habits for reed care and set a great example for your clarinet peers!