Use the last spoonful without mixing every tea
A nearly empty packet deserves a clear decision. Use a small remaining portion on its own before turning the cupboard into an accidental blend.
Look at what actually remains
The bottom of a tea packet may contain a different mix of leaf sizes from the top. Small pieces settle, and the final spoonful can behave more briskly than the earlier cups. That does not mean you have discovered a new tea. It means the remaining portion deserves a little attention. Check that the contents are dry and in suitable condition before deciding how to use them, and do not treat a suspect packet as an ingredient to hide elsewhere.
If there is enough for a smaller cup, make that rather than automatically combining it with another tea. Use the packet's instructions as a starting point and adjust the amount of water to the leaf you have. A modest cup can be more satisfying than a large weak one made to empty the bag. Keep the product label until you have finished so that you can still identify it if the last taste persuades you to buy it again.
Mixing should be a choice, not a disposal method
Two teas you enjoy separately will not necessarily make a better mixture. A strongly scented remainder can dominate a plain tea, and fragments may extract differently from larger leaves. If you want to experiment, combine only a small measured portion outside the main packets and write down what you used. Do not pour every leftover into one permanent tin and expect a repeatable result. You would lose both identity and the ability to judge the mixture sensibly.
Using tea in food is another possibility only when the product is suitable and the recipe actually calls for it. Do not add unidentified blends to a dish, especially when serving other people who need ingredient information. Nor should cooking be presented as a way to make damaged or spoiled tea acceptable. A good recipe is a reason to use tea; an unwillingness to discard a questionable remnant is not the same thing.
Learn something from the empty packet
Before throwing away the label, note whether you want the tea again and whether the original quantity suited you. If several almost-empty packets accumulate because nobody wants the final cups, buy less or open fewer at once. Finishing a tea can be a pleasant little conclusion rather than a chore. The next purchase will be better informed when the last spoonful leaves you with a clear preference instead of another anonymous jar.
