Efficiency is the key.
You're best bet is to tile textures wherever possible, and in the case of detail, tile the images in the X direction, allowing more room on the texture for other detail. Many of my buildings use 256 or 512 x 2048, with pretty much everything on the one texture (plain bricks in bottom section, bricks with windows just above, doors windows and bits above that, and then a roof texture near the top). An exception is made when I create large horizontal plains, such as grassy areas, concrete pads, etc., and there I'll use a single 256 x 256.
The above example (256 x 2048) could potentially yield a finished model with better resolution than if you had used several 2048 x 2048 textures, and what's better, all at a fraction of the pixel footprint!
Derek's "
doing more with less" approach sums things up nicely:
http://the-art-of-rws.blogspot.com/2012 ... uring.html