Why does a 10mb update take 2hr to install?
It's how Google does it's updates. They do A/B 'seamless' updates. It installs in the background and you can continue to use the phone then when it's done, you get a notification to restart the phone. However this method takes well over an hour no matter how big the update is.
I prefer the traditional method, where it'll just install the software from 5-10 mins depending on the size of the update then once the 10mims is up, you can use your phone. It's not 'seamless', as you can't use your phone while the update is installing, but then again, Google's method isn't really 'seamless' either as you still have to restart the phone and after the install you're sitting there with the Google logo and little bar optimising apps for a little while. If rather the update just be done with in 10mins.