No matter how small a project is, always purchase new wood stock first. You can then save the rest for a future project.
to make your trip to the lumber yard more efficient, pick up a few extra interesting pieces while you’re there. Don’t worry about taking a list of what is back at the shop - you can always use the extra on a small project
When considering if it’s worth using the stock you have, realize that you might need it for something later (also see rule 1)
Stop I’m already out of room!
Time to plan the storage addition. You’re a woodworker…just build one. :-)