Longer lasting spells

Allspice(The herb) is used to make spells more powerful, and increase longevity. Plus purple or black candles can be used for power in spells, which you can engineer into longevity or potency (So you get more uses out of it)

This one is used for sigils and I read it on "The travelling witch" blog. Draw a sigil or write a word on a seed, plant it and let it grow. The intention then manifests the whole time the seed/plant is growing.

Thanks for the advice guys. Good luck in your craft.