It seems that most knitters and crocheters don’t like swatching. Or, at least, the anti-swatching crowd tends to be more vocal online. If they do swatch, most people don’t tend to save their swatches in a scrap book.
Anti-swatchers will tell you it delays them starting on the “real” knitting and crocheting of their project. Or that swatches lie anyway, so why bother? If people do swatch, they often unravel their swatch in order to use the yarn in their project and not waste it.
Personally, I have anti-swatching tendencies, but my desire to have the sweaters I knit actually fit is stronger. So I swatch. I do tend to unravel my swatch so I can reuse the yarn, but I usually wait until the end.
I could not harvest the yarn from these Silky Wool swatches because they were made for a sweater being knit in the round. As you can see, I cut and tied the yarn at the sides, which meant there was no going back. (This is color 140-Rose Madder. It is an old color and might not be available any more.)
However, I was delighted to find them when I was rummaging around in my stash today! I’m planning to knit a hat for a friend, and here I already know what my gauge will be on two needle sizes.
Another option is to make knots in the tail left from your long-tail cast on.
It looks like I got 24 sts to 4″ on the US4 and 23 sts to 4″ on the US5. I also happen to remember that these swatches have already been washed and blocked.
Now, when I’m ready to start the hat, I can plunge in and cast on with US4 needles. All thanks to having these swatches laying around!