Reusing yarn

If I reuse yarn that has been previously knitted and blocked, can I use it with yarn from the same skein that was not used? Can I expect the brand new and previously used yarn to behave the same so that I get the same gauge? I’m wondering because I’ve been making gauge swatches for a project and I think I won’t have enough yarn for the project by the time I’m done with the swatches. So I want to know if I can frog the swatches and use them along with the new yarn, even though the swatches been washed and blocked. I know now that I should buy an extra ball of yarn for making swatches!

TIA,
Marge

Yep, don’t know if it will behave the same, but once it’s all knitted and blocked or washed, it should look fine. Many people reuse the yarn in their gauge swatches when they run just a little short.