Learning quickly that big Technic sets are not designed to be taken apart. I've disassembled the 42042, and 90% done with 42055. It's tough on the thumbs. Also, there are times where I'm completely stuck - as in, "what I have in my hand is indestructible and there are no parts I can remove right now without breaking something."
In addition, whoever designs these things is fully qualified to go out and get a job at a heavy-equipment manufacturer as a Senior VP of Product Design. Impressive - and I haven't put them together yet!