"Saving time" during the interview process doesn't make sense if you're going to spend the next X years being UNDERpaid at your job.

If we assume that your time has some amount of value, you are always better off withholding your desired salary.

If you want to see whether or not they're going to be a potential employer, ask them for a ballpark of what they're willing to pay. But there is no reason for telling them free information.