Here's a list of Return Policy Law by state. Here is Apple's return policy. Note this policy does not supersede any state laws, so you may get more protection in some states, but this is the guaranteed minimum.

Legally, I believe each transaction is an independent event. They're probably not legally allowed to deny refunds and returns that happen within their own policy and within the legal limits of each state. The sale is a contract, and Apple's return policy is a part of that contract.

Whether it's right or wrong for you to keep buying and returning stuff, my opinion is that you should have made up your mind the second time you bought one. The first time it might not have met your needs or you didn't like it once trying it in different settings. You did like it, though, and you bought another one. New MacBook Pros have been rumored for weeks and weeks now, so it's not like you just learned something new.

Now, Apple probably doesn't care. I doubt you'll even get a funny look when you're in and out of the Apple Store every week trying, buying and returning stuff. But whether it's right? No. Not in my opinion.

Also, we don't know if there even are going to be new MacBook Pros at WWDC. It's not out of the question, but it's not confirmed either. If there's nothing announced in June, will you continue to buy and return MacBooks until the next Apple event? Eventually, you just have to settle with something and say you like it. Worry about resale values for the next upgrade.

TL;DR: I don't think they do maintain those sorts of records. If they do, it's unlikely that they'll use them to deny you returns. In some states, you would be protected from that kind of activity. But I think it's wrong, and you should eventually just make up your mind. Apple might be able to use that purchase and return history later on (for repeat offenders) to deny a refund because you would be entering into the purchase in bad faith. If you bought it, it broke in three days and you got another and then return it, I doubt that's going to be an issue. In fact, you didn't get the full 14-day period to use that MacBook and see if it worked for you. But making a habit of it might land you in hot water, and it's not right. Make a decision, stick with it and enjoy your Mac!