The answer to this question depends entirely on the builder. A good builder will give you a pretty good idea of when you can expect your wheels because they'll "slot" you in once you put down a deposit and they know how long it will take to actually get the job done. Of course, if you go with a solo practitioner who does handbuilt wheels, you'll wait a little longer.

While the wait time you're talking about isn't unreasonable at all, I have an issue with any kind of business that isn't responsive to clients because it takes so little time to answer an e-mail.