The problem that i could see is that if you set a value to low, and offer reserved slots in return for instance. The people that actually donated might not be able to join the servers because there are people that earned it with loyal points. Basicly destroying a second donation of that player if he cant get in
even if i say you need 10days of connection time to get it, then still about 50 people have it. Its hard to find the correct "balance" when to give it out.