Herbal bath tea bags can be used 3 times within about 4 days.
You can use the same sachet for 3 days in a row but then to avoid 'spoilage', it's best to rinse the pouch out.
You can re-use these wee sachet bags. Just wash the material with non-toxic soap and it's ready to go again.
Additional options include adding powdered milk or 2-3 tablespoons of olive* or sesame oil plus 3-5 drops of your favourite essential oil. I like lavender or ethically wild-crafted sandalwood, rosewood, and sometimes rose geranium.
*olive and sesame are my favourites but good quality nut oils or vegetable oil.