7300 FastLane setup

so the problem with extenders is that you lose half your throughput because the extender's has to receive the signal and then rebroadcast that signal. What fastlane does is designate one of the radios (either 2.4ghz or 5ghz dependind on how you set it) for the extender to talk to the router and uses the other radio for rebroadcast. It helps prevent the throughput loss that extenders suffer from.  Problem is you loose one of the radios for usage.  

triband extenders get around this by using the 3rd band exclusively for that backhaul connection to the router. (or if hardwired, you can use the 3rd band). 

That explains fastlane. Now on your you're wanting max range. How far are we talking here? There is some optimization you can do such as centrally locating the router, optimizing wifi channels, moving routers/extenders to avoid hvac and other interfering metals, using powerline devices to help mitigating interference.

2.4ghz signals penetrate the best but have lower throughput because of this. Keep this in mind when setting up the extender as you could alternate either radio as the backhual for whatever works best for you.