Flutes of Renewal come in 6 superslayer forms, Undead, Demon, Reptile, Repond, Arachnid and Elemental. These have 300 renewable uses. The uses only come back every 5 mins if your logged in. Or if you own a house you can lock it down in your house... As your house is always logged in it will restore while your logged off.
Also a point to remember is once the instrument gets to Zero uses it goes poof so you need to keep a close eye on it.
These flutes came from the Treasures of Tokuno event a while ago and were classed as minors to be handed in for the Majors, You can still pick them up from vendors for 200 - 400k each on vendors (Europa) and i find them very useful.
Elf.