These greens are so good. I pick some every night along with the baby kale. Very prolific, easy to germinate.

These seeds are great. Planted 3 days ago and already have leaves growing

I purchased a package of these seeds (4oz?) several years ago (it's 2020 now, I think I bought them in 2016 or 17), kept them in the fridge. Started growing them again this winter in a small hydroponic system in my garden window in jiffy pots. To my amazement, they still have a near-100% germination rate! Lettuces are basically grasses and grasses are very tough seeds capable of living dormant for years in harsh conditions before they sprout.
I soak the Jiffy pot to expand it, then just dip the top into the seeds, about a dozen adhere to the top, then I cover in plastic wrap until they pop which is usually 3 days or so. They grow very quickly into a delicious variety of greens. I start 6 every 2 weeks and I always have more greens than I need. A lot of them get stir-fried, mixed into fried rice, pasta, etc. There are even multi-colored Swiss chard seeds in my mix, I've extracted them individually and grown them into full sized plants in my garden. Anyway, the value here is extraordinary. Buy a package and keep them in the fridge, you'll be growing fresh greens for many years.