Sure, you can wear old orthotics, but why would you?
It is generally not recommended to wear old orthotics because they may be uncomfortable or may not fit well. It may also be difficult to obtain the correct size. If you decide to wear old orthotics, be sure to replace them properly to ensure proper fit and comfort.
The better option is to seek out professional help in determining whether you need to refurbish your orthotics or get fitted for new devices.