I guarantee you that it is a good idea to use those charms. Say you had 1000 green charms banked. Making Fruit Bats loses you 39 shards (when you swap back in), equaling 975gp loss plus the cost of a banana and a pouch, for a total loss of 1006gp per pouch for 121.2xp. To get the 121,200 xp you give up by not using greens, you'll need 372 crimson charms. Assuming you get them from waterfiends (which are about 105 crimsons/hour at maxed melee with void and piety), you'll need to spend 3.5 hours camping waterfiends. In addition, you will lose 50 shards per pouch (when you swap back in), equaling 1250gp loss plus the cost of a granite (500g) and a pouch, for a total loss of 1425gp per pouch. Fruit Bats: 1,006,000 coins cost, 121.2k xp. Granite Lobsters: 530,100 coins cost, 121.2k xp, 3.5 hours. Money saved: 475,900 coins Time spent: 3.5 hours Money saved/hour: 136k coins/hour So if you make over 136k coins/hour (which you should be able to!), use your greens.