Sometimes it happens that skinning succeeds and you get one foot, sometimes two and sometimes none. Cooldown is 10 seconds after killing a rabbit. If yo skinning successfully and get 8 foots, and you only need 7 you can leave them for the next time. They don't disappear and npc won't take them.
Here is statics about this:
During the Rottin Wood and the Married Men Quest, 1941 trials.
Item | Amount | Percentage | Tries to get 1 |
---|
You successfully gather a rabbit's foot in excellent condition. | 978 | 50.39% | 2 |
Your attempt to skin the rabbit failed. None of the rabbit's feet are in an acceptable conditions to make a lucky charm. | 609 | 31.38% | 4 |
You successfully gather two rabbit's feet in excellent condition. | 354 | 18.24% | 6 |
Also, if you attempt to skin a Rabbit within 10 seconds of killing it, you will get the message "You have to wait a bit before you can skin this animal.", and when you gather enough rabbit's feet and have killed a certain amount of rabbits you will get the message "It looks like you have skinned enough rabbits for today."
source: https://tibia.fandom.com/wiki/Rabbit%27s_Foot/Statistics