Slow doesn't equal 10 hours. Yes it will be slow no matter what. But you aren't doing yourself any favors by making it even slower.

Between reformats and new computers over the last 4-5 years I've done 4 completely fresh downloads of the game into install and updates and none including across multiple computers including laptops have taken a over 5 hours start to finish. This has been with both terrible Comcast and way outdated modems which hurt and even once on slow as heck AT&T dsl ewww.