I had to do the same with my rainbow Thandi, the rhodesian ridgeback. She had been with goldens as a youngster and so we adopted one, but with 10 hours I knew it was a huge mistake and took the golden back to the rescue people. After Thandi died we rescued first Mika, a boxer/lab/heinz and a year later Chloe, a shep/rottie/bc and they live soooo incredibly happily together. Sometimes the older dogs just can't give up half of their space. You did the right thing.