We have placed our 10th foster in 18 months. We had Toby for 3 months, but we found the perfect home for him.
It is always bittersweet leaving them behind wishing you could explain that you aren't abandoning them. You just hope they somehow realize you have helped them by keeping them out of a shelter, or worse. You hope they realize how much you have cared for them and enjoyed having them be part of your family for the time they were there. You hope they know how much you love them despite the fact that you can't keep every one of them. You hope... I hope.