I think I understand the OP's question.
She wants to know if she should give a deposit, KNOWING that the wait for the pup she really wants could take more than a year, OR to forgo that route with this very reputable breeder, and select another puppy from a litter that has either been born already, or is due soon. Another consideration is whether or not the deposit is refundable, and what the time constraints on that aspect of the contract would be.
It's about how long she has to wait, with no guarantee of when this contract may be fulfilled, I believe.
If one is not specific about a particular breeder, and has familiarized themselves with other reputable breeders in the area, and waiting is not an option, than I would suggest one purchase a pup from a reputable breeder who has not promised the pups to anyone else.
I am sorry to hear of the loss of your previous dog. I can tell you don't want to wait endlessly for a puppy, which can happen with a deposit on a future litter, especially if colour and/or sex are important. Oliver was supposed to be a tri female, and he's a Blenheim male, but he was available, and I'm very glad. Henry was male, but a tri, and again, I could have waited, but the wait could have lasted forever.
I hope this helps.