Hi BSPHIPPS,
thanks for the kind comments 
In most cases … Black Friday sales are more about marketing than anything else (you can see more about “sale prices” in post #5 here).
The Restava listed prices are their regular prices.
Select foam also has a series of rotating sales that change in the name and details but the sale is ongoing.
Rocky Mountain also has their “normal” $299 off which is ongoing but I believe the 5% may be additional.
In some cases there will be minor differences at different times of the year but for the most part better manufacturer’s or retailer’s pricing is consistent throughout the year and any “real” sale prices for those who have them (and many don’t have any sale prices at all) have a fairly small additional discount.
There is no need to take on any additional urgency based on the time of the year when you are buying a mattress because the better retailers and manufacturers have good quality and value available every day of the year.
Hopefully you’ve read the tutorial post here which has all the basic information, steps, and guidelines that can help you make the best possible choice.
Phoenix