Traveling with two is more difficult. When I had just Couver, it was easy to toss him in his bag and off we went. With two, it is a little more of an ordeal to pack them up and go.
With two, the vet bills are doubled. We have been lucky and haven't had any huge health issues or catastrophes happen, but with two dogs, vetting is more expensive.
The same is true for grooming, bathing, food etc.
No regrets here though! I love having two
I know 3 would be too many because I have fostered and watched my mom's yorkie. I only have two hands, so three is one too many!