Projects take far too long to upgrade from earlier versions.

What is with the stupidly long times to upgrade earlier projects to more up to date versions of unity?

I am upgrading from 5.3.0b1 to 5.4.0f3 and its been about one and a half hours for a 10gb project to reach 20%. What the hell?

Why is it so damned slow?

Hard disk is fine i transfered the file to the edd in a couple of mins. The problem even persists on my ssd too. My question is what causes it to take so long. Its not converting formats is it? If its already in a unity readable format then it should go alot faster?

Secondly why not update? I backup my project beforehand. Plus the recent rendering performamce improvements are more than enough to warrant risk. I cant wait for the terrain improvement. Regardless if it screws up atleast i have a duplicate to revert to.