1. REI dividends last until the end of the second calendar year from when they are posted. So, for example, dividends posting now, from 2011 transactions, will be good through 12/31/2013.
2. You don't have to use REI dividends for store credit, but of course that's the easiest thing to do--combine them with your coupon. Beginning on 7/1 of the year they post, you can have them send you a check. Large as it is, REI is structured as a real cooperative, and its patronage rebates are real money.
3. Yes, for a change, this year the Member Rewards 20% off coupon, which officially kicks in on 3/23, is supposed to be good on full price, sale, and clearance items. There are as usual a few exclusions, but not many.
4. Do you normally only buy sale and clearance? You too can earn a dividend. Get an REI Visa card and use that for all your REI purchases, and you will still earn a 5% dividend on everything at REI. Earn 1% on everything else you use it for. No annual fee. I don't remember what the interest rate is because I never carry a balance. The REI Visa is the only way we REI employees ever earn a dividend, because of our discounts. My REI dividend, using the card for everything, runs over $600/year.
5. Furthermore, if you are an REI member and don't already have a REI Visa to use for your REI purchases (to earn your extra 5%), they are currently having a Visa promotion, through 5/31. Apply by then, get approved, make any purchase by 6/30, pay the bill, and you get a $100 REI gift card. Why are they doing this? Saves the coop a lot in bank fees! And they want to "add value" to your membership. (The employee whose referral code you use gets $40 too--so be sure to get it from your favorite REI employee.)