Yes depending on your application, application professional, if they had been taken care of, and they are removed properly.
Can I re-use my hair extensions?
Yes depending on your application, application professional, if they had been taken care of, and they are removed properly.
Trichologist / Cosmetologist : Kerri Jarrett 
you can reuse them as long as you take care of them. my clintele usually buys a new set after 6-7 months becasue they do get ratty. If you remove them soak them in fabric softner for 10 minutes then rinse thouroughly. They will be softer and easier to handle.