Congrats on the anniversary!

I can share my experiences with Zack. He was an only, very spoiled pup from the day I brought him home at 5 weeks old until just before his 11th birthday. Much like Tani in the above post, he has always been more interested in people than other dogs (he thought he was a person with 4 legs, so now with only 3, we'll never be able to convince him otherwise!) Then, one day on the way to work about 3 years ago, I found a boxer puppy on the road. I took the pup to the SPCA thinking some family must be going crazy missing him, but after 3 days he was not claimed. I took Zack in to see how they'd get along - the puppy wanted to play & be around Zack's face, but he was having none of it. So, we knew it wouldn't be a good fit. By then, we decided we wanted to be a 2-dog family, so tried some more shelters/other puppies. Finally, a volunteer at one of the shelters suggested an older boxer mix (about 8 at the time) who had just been returned to the shelter after 8 months with her pawrent (he had been chosen from a lottery to get her & then got a terminal illness.) We figured we'd give it a try, and they were a perfect match - Izzy tried to sniff at Zack's face once, he turned away, and then she did the same, and they've lived in relative harmony ever since.

They pretend to ignore each other, but there are signs of their co-dependence. Izzy has been mostly deaf since we got her, so she takes her cues from him (especially when we first brought her home & she was learning our routines.) And, I have photographic proof of them cuddling up (really it's usually just their butts touching each other, but we'll take what we can get!) When Zack was gone for two days for his surgery, Izzy didn't seem to miss a beat - but I've never seen her as excited as the night we brought him home. She actually jumped off the ground & then cried every time we took him out for the next day or two.

My advice would be to definitely try an older dog, and have the dogs meet in neutral territory - you should be able to tell within a few minutes how they'll get along. And, keep trying until you find the right one with a personality to mesh with Simon. Best of luck.

     I strongly agree with the advice here.  I'm a firm believer that two dogs are better than one.  They're pack animals on an instinctive level, and while you're the pack leader and the center of your dog's life, you're still a different species.  Like Cemil said, it's not always a play issue – dogs just like being around each other, even if they're just laying around in the same area and not actively interacting.

     I think having your dog meet with potential buddies in a neutral area is a very good idea.  And on the day you decide to bring a new dog home, don't lose heart if they're not instant best friends.  Our first two dogs were Shadow (a lab/border collie mix) and Max (a lab/husky mix), who grew up together.  Shadow died of a rare blood disease when he and Max were about six.  Max was absolutely devastated, and completely lost without his buddy.  So we got an adult dog (Linda, an English lab) to be his new friend.  Max was always kind of an alpha dog, so we weren't too worried about bringing Linda into into the mix.  She doesn't have a dominant bone in her body.  Linda was the best thing that ever happened to him, although they didn't interact much for the first few days.  But having a new dog around the house instantly improved his morale, and it wasn't long before they were inseparable.  I think it made a big difference to have Linda there as a buddy when Max got cancer and became a tripawd.  It's always nice to have a friend around when you're not feeling well.  There were never any issues about Max's suddenly missing leg.  The most Linda ever did was give him a curious sniffing when he came back from the hospital.

     Once Max died, we didn't want Linda to be lonely.  She has very little interest in other dogs, and probably would have been OK if we had kept her single.  But we like having two dogs, and we didn't like the idea of leaving Linda alone if both of us were working.  So we got a puppy named Bernie, who Linda absolutely loathed at first sight.  For the first week, she actively avoided him, and snarled and moved away whenever he tried to get near her.  We thought we'd made the worst mistake ever by adopting him.  But about a week later, Linda surrendered to the inevitable and started to tolerate him, then finally started playing with him.  That was about eight months ago.  Bernie is still a horrible little monster and a complete menace to civilized life, and he often annoys Linda (and us) to the point where it's a miracle we don't throttle him.  But they do love each other, and they'd be lonely if the other wasn't around (especially Bernie, since Linda is his favorite toy).

     So yes, get another dog.  I think the one you have already will be happy about it in the end.

Trouble had been an only dog for 11 years when we brought Duke into the mix.  We were super cautious and did a LONG drawn out introduction.  It was literally weeks before we allowed them together.  Duke was crate bound for 2 weeks just so Trouble would be used to him being in the house.  After that he was tethered to one of us constantly when he was uncrated for about another two weeks.  Then we left him to drag his leash for another week or so.  Just in case we needed to quickly stop him, we could grab the leash or step on it. 

Duke LOVES Trouble.  She is his buddy and he protects her - even from us!  Trouble more or less just tolerates Duke, and makes sure he doesn't get more attention, treats, or toys than she does.