Some like to have actual estimated times until a transaction, such as a buyer is planning on a purchase within one to six months. The only problem with this is that the field is aging from the moment it's entered. Thus you can't look at this prospect three months from now and know where they are in the process. A simple system that's worked for sales persons for ages is the Hot, Warm or Cold status. You arbitrarily assign the client to one of these groups. This is based on your experience and communications with the prospect.
Here are some possible groups that would reside in each of these classifications:
Hot - Being shown properties, requested documents, listing appointment made, etc.
Warm - Regularly corresponds, researching specific properties, on a new listing notify list, etc.
Cold - Gave contact info on web site, emailed for listing info, called in about a listing, etc.
Once grouped this way, you can plan your daily marketing activities around the status of the prospects. You might plan on calling hot prospects every x number of days, while emailing, mailing or calling warm prospects every other week, and keeping cold prospects on drip email or direct mail marketing lists. By focusing your efforts on the prospects closest to doing a deal, you maximize use of your time..
Part of the Contact Management Training Series - The Whole Series:
The Importance of a Good System
Contacts and Prospects - The Difference
Don't Use The MLS Solution
Protecting Your Contact Data is Critical
Using a Prospect Type Field for Efficiency
Sourcing Prospects for Profit
Using a Status Field to Help with Marketing

