NO, NO NO, NO NO! It's not fair to the agents, AND it's not fair to you. You will never get the best of any Realtor if they don 't feel you are consistent and loyal. There is a relationship that develops whereby your Realtor of choice really learns about you and your preferences. That will stand you in good stead as you pursue your search.
Once I really know my clients, I will do previews, make calls for off the market homes, and do things that I won't do with a casual, not too serious client.
If despite the feedback you receive, you do choose to work with more than one agent, I suggest you at least be honest with the Realtors whose time you take up.