In the 747, I've found that the lightweight Telex headsets work okay, but my hearing is far enough gone that I sometimes have a hard time understanding everything. I don't do well with hearing in one ear only, so a headset which reaches both ears is a big plus.
The Bose X works great in the Classic 747, and the battery life is no problem at all. Cocking one earcup off the ear slightly isn't a problem, and just moving it slightly to one side is enough to hear conversations in the cockpit.
A headset with which I've been very impressed is the Uflymic, used with the Bose Quiet Comfort QC-2 or QC-15 noise cancelling headsets. I have one and use it with a QC-15. It works very well. Battery life is on the order of 30+ hours for a single AAA battery. It's a compact arrangement that can take up very little space in a flight bag. It's also very affordable.
I picked up a Bose X on ebay some years ago, and it's seen all kind of abuse around the world in piston cockpits, turboprop cockpits, and in turbojets. It's suffered in the heat in the sun in the middle east, and been bounced off canopies in the mountain west, and still works like a charm. The only complaint was a ticking in one ear, which went away with a new set of ear seals. In fact, I stopped by a Bose booth at Sun & Fun a few years ago, and was talking to the factory representative about how well the headset had held up in the abuse of a blazing hot cockpit in the middle east...and the bose rep handed me two new ear seals and told me to try them, see if they improved the little ticking noise...no charge. They worked like a charm.
The uflymic arrangement is nice because it's extremely light weight, very clear, and reduces fatigue on long flights. It can be used when riding somewhere as a passenger just by inserting a different cable, that comes with the headset. The mic has a music input, or one one can order the mic with a backup set of earbuds which are fully TSO'd. I carry the extra earbuds. It's proven to be a very reliable, very comfortable, very easy to use headset with far better sound quality and clarity than any other headset I've used.