Gotcha. ToEE and ToA (but not the first three) are developed as kind of "boardgame campaigns" where you play a "mission" that moves the story along a bit further. There are probably a dozen missions in each box, each taking probably 60-90 minutes.
This fills the niche for me for a quick "dungeon crawl" style session, without much potential for roleplaying. I use them when certain members of my gaming group can't make it, because this is pretty easy to pick up and play with whomever you have on hand.