This question is probably been asked out plenty of times, according to a general observation I have recently made. To me it seems like people tend to misunderstand things about this subject and get the wrong idea about it, and some people do not even get there answers due to the misunderstanding . I have seen some threads which give wrong ideas and answers, which probably happens because we certainly have some confusion and a lot of misunderstandings about spell casting, ritual works and of course that their basic form of working ; energy and energy manipulation. The confusion only grows and grows every day, so what we need is to get to some understanding about this subject and then answer this question properly.
The first thing we must do is to be aware of how spell casting works, and be aware of what happens after we do it. The importance of understanding spell craft and its affects is really important here because this question basically talks about spells casting, and from its content I can easily understand that the idea of spell casting is misunderstood. It's important to be aware of the main idea of spell casting because that's what the question focuses on, and its the only thing I can tell you in order to make my answer for your question more understandable, organized, and of course that more explained and detailed. Without mentioning how things work we can't even give out a proper and correct answer, so that must be done. Such explanations actually might contain the answer itself, so be focused and pay attention. ;)
While casting spells you basically use your energy and direct it for accomplishing and achieving your desire depending on your intent.
People mostly say that one can cast plenty of spells without any problems because they think that spells are simple 'power chants' that make everything possible for you and require no energy raising and dedication. This is the biggest misunderstanding here. People that tell you that magic is like Harry potter or science fiction movies are totally wrong.
When we get to understand that spells are basically about you raising energy and direction it for a determined intent or desire specifically, we already know the answer of this question if we detail things a bit more.
What people need to realize in order to understand this question and know its answer is that energy is not a toy to play with, as many people think it is.
People might think that energy is something we can use endlessly and play around with just as we do with our toys when we are in kindergarten, which is a very wrong opinion and a huge confusing misunderstanding in spell casting and energies.
Energy is something we need to take care of, be careful with it and obviously pay attention to it.
After understanding how it works and that energy is not like a toy, we can realize that after we cast a spell and we raise / dedicate our energy in a proper and serious way, we do not just play around with things like a game. We take a serious action when we do it.
Thus, casting a spell is something serious. If you really cast one and not just chant something pointlessly without knowing what you're doing, you will know that you can't do it too much since energy does not come that easily.
You need your energy for spells, to say it shortly, which does not come like candies, as I sadi.
However, I think you can cast enough spells in order to get satisfied. =)
Hope it helps,