Files served from non-cookie domain

Hi there most awesome support ever!
I have gone through the process of implementing hummingbird on my site, running tests, fixing things – things look pretty good -scoring over 90 on hummingbird for desktop and A’s in both pagespeed and yslow tests on GTmetrix. I’m now into the super-fine tuning and have the following 3 issues that I need help understanding better:

1. Browser Caching – recommended google setting is 1 year for expiry, mine says its set to 10 years and I can’t seem to change this with WPMUDEV hosting on the NGNIX server – am I able to change this somehow. If it stays at 10 years expiry what is the impact?
2. In GTMETRIX report, I am getting the following recommendation under the YSLOW tab:

Use cookie-free domains	
There are 4 components that are not cookie-free

I have no idea what to do with this, how can I ensure these assets are served from a cookie-free domain?
3. I forget my 3rd question – if it’s important it will come back to me! :grinning: