In the almost 120 films I've mixed, I can count only one where we didn't have anything in the LFE.... and weirdly enough, the one I am mixing now will only have LFE during the WB logo at the beginning... to be technically correct, however, even if it says "5.1" that doesn't mean it will have information in all 6 channels (it's rare, however, if it doesn't.)
There is usually LFE on most scores, source music, and of course sound effects/design as needed...
I low pass (24db/octave slope) everything I feed to the sub at 120Hz at the console (so do most mixers)... most encoders also brick wall the LFE channel into the encoder..
Noah.... please take no offense to my following comments, but in doing research on the Danley, it amazes me how it can be considered a desirable sub for anyone who is serious about accurately reproducing film sound tracks... there is so much information in the 1/2 octave between 80 and 120Hz it seems a bad choice for anything but rattling the walls and breaking plaster... from the LFE channel we only have a max SPL of 110db.. a product like the Danley is missing out on a lot of what is in the LFE track and accentuating alot of what isn't meant to be heard at the extreme SPL numbers it puts out... just my opinion.
While it might sound cool, there is nothing I see in the specs or frequency response graphs that indicates it is a good match for some one who wants to hear tracks as I do on the mixing stage. (and I have 12 18" subs on my stage for the LFE channel alone (with another 6 handling low end extension to my main LCR's...))