I have to agree about having 2 dogs. With 2, you have "dogs" instead of one special friend, but it's so much better for them. Our schnauzer still hasn't recovered from the loss of our big dog last winter. Neither have I, to be honest, but we aren't in a situation where we can get another dog right now.
Sybil, I have to say that in my experience, you will know when the time is right. Sometimes (and for some people), it's best to hurry out and get another pet right away. Other times it's better to wait. Either way, you will know the right time for you.
And no, it will never be the same as it was with Flossie...we only get a very few chances at that kind of bond with an animal in our lives, and they should be treasured, but that doesn't mean you should pass up the opportunity to have a different special bond with a different animal.
On another note, there are some days I wouldn't mind re-homing our electric-cord-eating, dog-whipping, bad-tempered demon cat....