So last session I started running Beyond the Crystal Cave. I substituted Tantamar in the Lhazaar Principalities for Sybarate, and the Eternal Garden is located in Thelanis, but otherwise I've not changed much.
We managed to get through the preliminary stuff and then the PCs fought their way through the Cave of Echoes. We finished just as they all stepped through the portal to the garden. Although there's not a lot of combat opportunities in the garden itself, I still expect it to take us about two sessions to play through it.
Once we finish this adventure, the PCs will gain a level, and I'll run the next Golden Vault adventure (Vidorant's Vault).
I'm also thinking I'll end this campaign around level 12, as there's not a lot of content to use after that point. (The final Golden Vault adventure is for level 11, for instance.) I would like to use the Ruined Colossus section from Vecna: Eve of Ruin, but I'd probably have to downgrade it a bit since it's for level 13.