I can't say I know anything for sure since this is my first year growing icebergs (I let DH talk me into it -- he told me he won't eat any other kind of lettuce
) But I just hardened off and transplanted out my lettuce collection, so here goes. First, make sure you added extra lime or granite dust or wood ash to the soil mix as they don't like acid soil.
Now, from what I've seen, the classic iceberg -- I'm growing a variety called Summertime -- is more "delicate" than leaf lettuce, batavian, butterhead, or baby romaine. Even a red variety summercrisp (which is another name they use for icebergs since they got a bad rep for lower nutritional value) called Red Glacier has held up better to the two stages of pricking out/up potting and transplanting out I've done so far. All the others have resumed growing and are looking happy. Also, when we had a bit of warm weather, Summertime, despite it's name and reputation for heat resistance, looked wilty -- it perked up with a bit of misting and cheesecloth shade.
When we had a particularly windy day, one of the Summertime transplants got knocked down and lost a leaf when a bit of STRAW