There should be some kind of withdrawal penalty like :
- 1st withdraw 1 mn penalty (you can be stuck by something, it happens and 1mn is not long)
- if you withdraw again in the next 5/10 mn window then 5/10 mn penalty (really finish what you are doing)
- if you withdraw again in a 5/10 mn window the full penalty of 30mn (you are not serious)