This is a very good topic...
As you all know I own MANY birds!! So I guess you could say I have MBS, however I do not take in every bird offered to me and give each one careful thought before I add it. I have turned down parrots that would be great for Shane and I because I thought they could negatively impact my flock..I always put my flock first. I firmly believe that each of my birds gets the attention they need, and yes I do believe I can handle a few more yet. But I am home all day also, this is a big factor. I can afford the vet care they need...I have a bird emergency fund. It had been cleaned out many times and replenished very quickly. Shooot last month I spent well over $2000 on vet bills and never gave it a second thought. Could I of used that money for things shane and I needed? Yes, but I took on this responsibility and its one I am serious about. My pets come first, no doubt about it. Shane and I would eat Mac N cheese if we were broke just so we could feed the birds what they deserve. In fact $ was tight this winter and we ate cheap food, while the birds got everything they always have, the best pellets, fresh food, etc.
I guess the point im trying to make is just know YOUR limits, everybody are different. Now I have a ton of birds, so do I get much alone time ever> NOPE. But I enjoy giving up my time for them all. I have a lot of "problem" birds, they take even more time and patience. But we always get through it! Anyways how many birds you can handle is up to you and you only, as long as you can care for and provide all the birds with what the need and lead a normal healthy life yourself.