Not completely true. You can hold only one Good Bee at a time (you can hold multiple regular Bees if you wish), however when that Good Bee dies/gets lost/runs away you can always go back to that same cave and get another Good Bee.

You want to learn another Secret? Everybody knows that Mothula can be hurt by the Fire Rod and Sword. Not many people know that Mothula can also be harmed by a Good Bee (I've done this on the SNES version, I don't know if it works on the GBA version). I noticed this when one day I was fighting him, and I ran out of magic (and potions), so out of dear desperation, I set my Good Bee free, just to see what it would do. Booyah, the bee bashed the moth. It's not the strength of one's size that matters, it's the size of one's strength

-BGS