How old is too old to change a dog's name?

I was just curious as to what age the dog would be too old to learn a new name. My dog is 10 and his name is Travis (I chose it when I was like 4) I don't mind it and I don't want to change it because everyone else would probably keep calling him it but can he have 2 names? Like a nickname that only I call him?Or would it be too confusing for him, because I love the name Sirius for a dog!