Field Charms do not accumulate in my inventory. I get to use it once a day.
Field charms do not accumulate in my inventory, even if I do not ever use them. There is only ever one (or zero) of each in my inventory. If I want to use 2 in one day, I have to make sure the charm slots are empty, and only THEN complete the daily task that gives that reward. If I do not have an empty slot where the charms go at the time that I accept that daily reward, I lose each reward charm that did not have an empty slot to fill. There is only ever 1 or 0 of each in my inventory each 24 hour period.