Circular needles come in various length, and this can become a limitation. The good thing is that stitches can squish up very close together, so you can get lots and lots of them on one needle, and it won’t hurt at all.
However, it is my belief (and it’s only my own personal belief) that 16-inch needles are not worth much. They are so limiting! You cannot do much with them. I personally find them so constricting when using them – I need more room.
That is why I say that you should only get ONE length of circular needles, and use them for everything you knit. Yes, you can. I use 40-inch needles all the time. There is no need at all to get a whole series of lengths – too expensive! The long circs will work for all the knitting I do, from sweaers, to afghans to fingers on gloves!! They can do it all. I really don’t see the point of having needles in various lengths. However, that is me. If you want to spend money needlessly on needles of all lengths, go ahead. (By the way, I have a really nice bridge I could sell you – cheap!)