(Please note - Here I am referring to Wood Betony - Stachys officinalis, formerly known as Betonica officinalis, a plant that comes to us from Europe. It is not the same plant as Pedicularis canadensis, also known as American Wood Betony. If you are looking at commercial sources, it is essential to ensure you know which you are getting, as they do not have the same uses.)
Regular readers will know that I'm a fan of the Doctrine of Signatures (see top bar), and also that I do crazy things like let plants instruct me on how to prepare and use them .. so the following is an example of how those sorts of things play out in my world.
I'd been drinking betony leaf tea off and on throughout the summer, "keying it out" over a period of some weeks. ("Keying it out" is herbalist-speak for getting to know a plant's personality.) I made a very mild brew, just 2 or 3 leaves fresh from the garden to about a litre of freshly boiled water, steeped for about 10-15 minutes. I added a couple of tablespoons of that tea to each glass of water I drank throughout the day, so each batch lasted me a few days. See? Not very
much betony in my system at any one time, but enough, and
for long enough, that I could get a sense of what its more subtle effects might be.
I dunno if that's what other herbalists and plant folk do, it's just the way I like to do things.