I TOTALLY understand that feeling! Snickers and have never been apart more than a day...and only for his medical reasons. When I had to leave him in the ICU at UT overnight once, it was soooo hard (even though I knew he would have the best care and someone watching him 24/7, I still worried and missed him). Leaving him for the day at the vet's for monitoring last week was also more difficult than I would have expected...he's trying to escape from the vet's wife, who is holding him and get back to me....
Like they know your leaving them...do they wonder if you are coming back? That breaks my heart to think about it, because you can't explain to them what's happening.
Is it that hard when you have skin-kids to leave them??!