IDK about sales, but following because we're going to need a ton soon! They semi-frequently do 30%, and if you see 40%, JUMP ON IT. That's as good as it gets.
I use SW Duration in matte pretty much everywhere. Halls, kitchen, bathrooms, everywhere. It cleans up beautifully with a magic eraser. We're currently prepping our house to sell and I'm really impressed how little painting I have to do, mostly just wiping down the Duration paint.
I have used SW Emerald when I was painting a room while pregnant, because of the lower VOCs, but as long as I can open windows and have no baby on board, the extra $ for Emerald isn't worth it to me.
I mostly use Duration on walls. I love the matte finish which is only available in Emerald and Duration IIRC. I use Pro Classic in satin finish on my trim/doors/cabinets.
I did use Superpaint once, and I don't know if it was a bad batch but the color wasn't fully mixing, and I wouldn't use it again.
They do have sales fairly often, 40% off is the best I've seen. They also pretty much always have a $10 off $50 coupon on their website that you can stack with the discounts.
Try using Mineral Spirits and elbow grease, that should get the paint off of the trim for you.
We use the Emerald in the Satin Finish for our entire first floor and I've been very happy with it. I've definitely seen 40% off sales a few times a year, and I could be wrong, but I'm pretty sure that they always have one some time in April.