I think the 30 day period that you must wait after changing your donation is a little bit excessive. I don't know if this is a marketing trick to get us to donate to get a different vehicle faster but it should be reduced by a bit. Down to either 15 or 20 days.
Sometimes you just would like a different car to have at your location or maybe you're in need of a plane, there aren't many downsides to us the ''community'' if this would go thru.
Yet everything about this is ultimately up to the SAES HQs.