Usually depends on your marketplace demands. Corporate policies often require 2 or 3 quotes. Many metro areas need very fast turnaround.
The only ones who need immediate pricing are usually tire kickers. If they won't spend the time to give you all the necessary information for a proper quote, they get the ballpark pricing and they are informed on what will affect the pricing.
Quotes like the one mentioned usually have a set of specifications you have to follow and are handled through email. You have all the info and plenty of time for an exact quote, If not a few follow on questions. In these quotes, you can use words that will help raise questions about other company's quotes, and offer options for cost savings.
"high-performance cast vinyl with a protective high-performance cast laminate $xxx.xx"
"premium calendared vinyl with a protective laminate $xx.xx
By using certain buzz words you can call into question what materials your competitors are using and help make sure they are comparing apples to apples.
I have a friend who says "all quotes start at a million dollars. every piece of information you give me will get us closer to the actual cost."
Another quote for Design time is "design is like a cab ride. if you know where you are going we'll go straight there. If you don't, the meter is running until we get to the destination."