When you're ordering a meal in a restaurant, you've got a pretty good idea about how long it's going to take. You've also got a very good idea of why you're there in the first place: you want something eat and you fancy whatever food it is you're choosing.
Things aren't so straightforward with ordering something like a logo or creative consulting. That's why "how long does it take?" is one of the questions we're most frequently asked. (I'll tell you the most frequently asked next week.)
Here are some examples:
A logo takes from two weeks to a month. This includes initial consulting, design, alterations and delivery.
A brand identity takes anything from a month to six months or more because there's so much more involved.
Consulting can be from an hour or week to ongoing.
I used to say "it depends on the project", but I wouldn't like to hear that myself, so I stopped using it.
In all honesty, somebody who's working professionally really should be able to give you a clear estimate of time. Ideally, that estimate should be readily available to you without needing to ask.
At the very least a deadline should be set immediately. Let's face it, you wouldn't eat in a restaurant where the waiter says "I don't know how long it'll take."