There are some fan-made "Adventure 7"s out there you could try (such as Ron Lundeen's "Mhar of Leng"). You could also run Wrath of the Righteous as an "Adventure 7" of sorts.
Otherwise, you're on your own for continuing those characters. My recommendation is that you don't bother, and start new stories with new characters. There are so many neat characters in PACG, why stick with the boring ones you've already played a bunch? ;)
If you want to get more mileage out of your Rise of the Runelords box, there are also fan-made adventure paths (such as on the link above), as well as the Season of the Runelords and the mini-season Season of the Goblins (meant to be played with goblin characters, either the promo ones or from the goblin class decks, but you can play it with anyone). All of the organized play seasons are significantly more challenging that the scenarios included in the box. Play them with brand-new characters, though, and you'll want to download the free guide to organized play in order to read up on the tier system so you don't fall behind on feats (even if you don't follow any of the other organized play rules, you'll need to get feats when you normally would as if you were following the tier system).
You can always start the next adventure with the same characters if you like them, but you have to reset them to start (no feats, random basic level 0 cards...).
May be a way to try allocating feats (skills, powers, cards) differently
