Yeah, I don't think I have heard the ES10 sound signature change ever since I got them.
The biggest changes have been switching earpads, using EQ, and use amps with EQ switches.
Talking about which, I just found my old C&C BH portable amp today. Pairing them with my ES10, I can only say... "wow". I have never heard this sort of soundstage before in any closed headphone. It's easily larger than some open cans that I have heard recently... namely the HD 650 and DT880.
I can't believe it. This late into ownership, and I still haven't heard everything yet!