Led lighting. Extended lengths
As Dan says, there is a maximum to the number of connected segments you can run. After that, you can get "RGB amplifiers" that are powered, and run the next set of segments. 



You should take into consideration:


The max length of a segment on a single power source (as published by the manufacturer)
The size of the power supply needed, and the space you have for supplies
The cost of amplifiers and power supplies 


It may make sense to have several small(er) power supplies rather than one or two large ones.