So now you've researched herb/color/spirit/wood/whatever associations for your spell, put together some wording, gotten your gear together, and done the spell once.
Should you do it again? If you want to do a spell for the same thing again, for that matter, do you need to rewrite it or somehow 're-acquire' it, as in D&D and so many of its offshoots?
Well, let's deal with the second question first - you don't 'use up' the magic of a spell by doing it. Real life is not a D&D game.
Some spells you do once, and you're done. Parking space spells, for example. You need a space, you do a quick chant, you get your space, you say thanks, done.
Some spells get done more than once to be effective. I suppose I was first exposed to that in Raymond Buckland's first "Candle Magic" book, where for one spell I did I recall doing it for 7 or 9 days, moving the candles closer to the center each day.
It's not uncommon to repeat a spell for 3 days, or 7, or 9, or 13, or a whole moon cycle or whole season. It's also not uncommon for those longer-running spells to tweak them along the way. Maybe swap an herb or two, or an incense or oil. Maybe vocalizing differently - vibrating in a different key, singing instead of saying, what have you.
As always, record what you changed, and why, and the results in your BOLS.