I like Beyond for the convenience - making and tracking characters, cross-links to items in other areas, encounter making, combining books into one section (such as under the "Spells" and "Monsters" section) and the like. But I treat it as a supplement to the printed books, as I know I'll have the books long past the end of any edition. I do remember when the electronic subscription for 4E went away and the electronic books for it did too, for example (yes, they're on DriveThru now, but for a while, they weren't, and you'd have to rebuy them). I do wish that WotC would do the "buy the book, get the PDF/Beyond version for free. Or at an extremely discounted rate.
In the case of those free adventures, I've used copy & paste to put them into documents for my own use in the knowledge that I'll still have them the day they vanish along with Beyond. Back in the 3E days, Wotc used to do dozens of web supplements, and I've saved off all those too.