Turning it on / off on a daily basis will cause the line monitoring software to assume there is a fault, and will reduce the signal speed in an attempt to compensate.
Sorry but that's a myth, From my earlier post.
I turn my entire system off each night, I very rarely have any serious problems with any of my kit. It means that the functions are refreshed each day so that any minor corruptions in memory are removed. It also means that you change your ip address every day (assuming you have a dynamic address.) which can be a security enhancement. Despite what some people on here will say, it makes no difference to the speed, it's a reasonably solid 7Mbs or so even immediately after switching on.