I don't and haven't worked for Sleep Number but the business model is pretty transparent.
Give Yourself a 3-4 Month Window To Buy a BedThe Sleep Number people want you to buy a bed now. They'll tell you the best sale is right now but the truth is that all their sales are pretty similar. It's your job to take a look at them from a wider view.
Visit a Store with a Reliable AlibiGet into whatever mall has the Sleep Number store and let the sales person give you the whole 9-yards and let you lay in all the beds. Come into the store knowing you are NOT going to buy a bed. You'll get less of a hard sale from the store if you tell them why you can't buy a bed (you could be closing on a house or moving to a bigger apartment in 2 months and don't have room to store it). Figure out which range of mattresses you prefer. Thank the salesperson for their time as you leave empty handed.
Visit the WebsiteThere is no good reason to buy your bed at the mall store. The prices and discounts are the same and you won't get the hard sell on a new pillow or accessory. Now that you know which mattresses you liked start looking at prices. Ignore the discounted price for now, and assume you'll buy it at full price (but you won't). Still feel good about your possible new bed? Excellent.
Get Historical Discount DataRemember how I told you to ignore the discounts? That's because they are useless without historical perspective. Does Sleep Number want you to get their historical discount data? They want you to think there is no discount like the discount today. Fortunately, they have a Twitter account dedicated to promoting current deals that you can use to harvest historical data. Did you notice that they tend to have a different mattress on sale each month? Add your favorite mattresses to the cart with and without bases to see how the current discounts size up. Odds are if there is no discount or a weak discount next Month will be better.
Realize the Base is a ScamYou may have noticed that there is some fluctuations in the the discounts, and that's to be expected in day-to-day marketing. But the bigger changes come because sometimes the discounts are on a "bed" and not a mattress. That means you might only get that $600 discount after you purchase the $300 base. Unfortunately, using only the Twitter data doesn't give you these numbers, but looking at larger trends you can make some estimated guesses.
Did I mention the Base is a scam? for $300 you get a big hunk of plastic. For $150 more you can get some legs on it. For less than that $450 you can go to Ikea or Wayfair and get a nice looking platform bed with a headboard and everything.