I don't think age is as high on my list of considerations as other factors is. Personalities and temperaments are definitely the deciding factor in avoiding a lot of problems that you will have to sort out and deal with. I would not get another extremely dominant, pushy, headstrong dog to incorporate into my group at this point. You know what your dog is like and have a good idea of what is going to work for you. If you find one you like, such as the Saint, take your dog off property to a neutral place for both dogs. Let them meet, do the sniff greetings, watch how they interact. If you are comfortable with that, try to find a place where they can both be safely offleash, but not on either dog's familiar territory. If that works, have them meet up a block or so from your home and walk them home together. Take them into your house and yard, then let them off leash and watch them. This is what I have done with mine and it has worked out great. I have never had just one dog at a time for more than a few months. I like for my dogs to run and roughhouse with each other, not me. Good luck and remember that not every dog you like will be a good fit for your dog. I believe any dog can be incorporated into any home, with enough time, patience and effort, but, I am not willing to spend that kind of time, just to create harmony, when I can spend that time on training, obedience and fun things with the boys. I wanted them to like each other, so I tried out a number of dogs before we all agreed on Jake. By tried out, I mean had different dogs from different rescue groups, that they met to see how it went. I didn't adopt any, just had them meet up with them and brought a few to the house. I picked the breeds I liked, and narrowed down their choices of dogs, but they got to pick the individual dog.
Kathy