Let's say a puller just brought a Rappelz mob to your party, but they're badly hurt and you're afraid they might not take even one or two more.
What do you do in Rappelz Rupees?
1. If you used your full heal spell, sure, you healed them, but then everything that was on them is now on you and, oops, you created too much threat for the rest of the group to pull them off you quickly enough Rappelz Rupees.
2. If you had used your lower level heal, it would be far easier for someone else to hit one of the mobs and pull aggro.
3. You can always use another lower level rapid to heal the puller again, if they need it.
4. But by splitting the threat into two parts like that I have often kept a puller healed without drawing aggro myself where other clerics have pulled them all on themselves.
5. as I said in the MP Conservation section, you should always be seated unless you're actively healing in that moment. Likewise, you should always have a spell potion activated to increase your cast speed.
6. If you want, tell people that you'll donate less force chips to a party because you keep those active to Rappelz Rupees.
Buy them from the store or the deluxe spell potions from other players. The best clerics at high levels generally all use deluxe spell potions all the time.
7. At lower levels buy the normal spell potions from the vendors - they're much cheaper.
8. On Lydian server, I've only seen a small handful that do, though - but they're the absolute best healers on the server. It makes a big difference.
If you were planning on sitting up and using a lower level heal, but heal isn't done recharging, then just wait for it and use a level10/8/etc heal instead.