Trying to decide if I should get another Cocktiel?

We unexpectedly rescued a cockatiel from a tree outside my work almost 2 years ago. We put ads out but no one claimed him so instead of taking him to a shelter we decided to keep him & named him Harley. Did alot of research when we got him because I've never had one before and since then we have become to love him to death. His previous owner must have been kind to him because he is mostly hand tamed and loves to be out of his cage, however, he doesn't get out of his cage as much as he used to due to our schedules and us already having 4 dogs so we need to have Harley in a separate room when we do take him out. My husband is at home most of the day so Harley does get at least an hour out a day and on the weekends I spend at least an hour a day with him. We also put him in our living room during the day and in our bedroom at night so he is always in our sight and we also communicate with him throughout the day as much as we can. However, sometime I feel guilty that he is still not getting enough time out of his cage. When he is out, he doesn't really explore. He pretty much stays on our shoulders but lately he is not wanting to go back into his cage when its time. I do not know if he came from a home with another bird or not. Me and my husband have contemplated getting another one for about a year now but are torn. I have read that if you have 2 birds, then they will bond more with each other than with you. We certainly don't want that. However, if we did get another would it be acceptable to permanently keep them in separate cages. I really don't want to house them together. I don't mind the extra cleaning work, but what if we put their cages side by side and they seem to get along and then get frustrated because they can't have contact with each other. Would that stress them out. Any suggestions would be helpful.