I'd go a step further than Brad. I'd divide the run into sections between six and ten feet long, and run power onto the tape every six to ten feet, whatever you decide. The important thing is that you don't cut the tape into those sections and power them. You actually add power connections at each of these points.

His first point cannot be overstated, but let me be less subtle: if you can see ANY reflections of individual points of light, even faint roundish spots, your lighting will look like cheap trash. Don't light up a reflective surface without using some kind of diffuser, even if it causes the lights to be dimmer. Extrusions keep you from seeing the lights directly, so they're great, but it's sometimes harder to avoid seeing a line of hot spots reflected off of a surface.