I was reading this excellent site http://www.goodui.org/ when one of the points made me think
Repeating your call to action is a strategy that is more applicable to longer pages, or repeating across numerous pages. Surely you don't want to have your offer displayed 10 times all on the same screen and frustrate people. However, long pages are becoming the norm and the idea of squeezing everything "above the fold" is fading. It doesn't hurt to have one soft actionable item at the top, and another prominent one at the bottom. When people reach the bottom, they pause and think what to do next - a potential solid place to make an offer or close a deal.
While I think this is a good solution in which you have a reasonably sized page where you can reach the top or bottom in three-four scrolls, what if you have a really long page. Do we really know if users will scroll all the way to the bottom and then make a decision ? In that case wont it be better to have a floating call to action button which allows them to do an action at any point of time ?
Please do note I am not suggesting this button should hide any text or content but it would float at the side where it is visible but not in the way.
Please note I did see these questions and go through the answers in detail
However they don't apply to my question specifically.