V.I.P should expire within a year or so after donating.
That's how you will make money. If the contract expires their gonna either want it back and donate again or they wont. If they wont,it just means they didn't really enjoy it in the first place,so who cares. If they want it,they will buy it. Thats how server-hosting companies make money,once you pay,you are given a time limit to pay up again. Simple.