I would just cut the object that you want to tile say 1/4 of a texture on, and apply the tiling part to each cut section of your geo. I can do a quick example tonight if that isn't clear.
Right. Everything has a cost for sure, just as more texture lookups will incur a cost. Cutting up the geo in that way would be a bad way to deal with say, a floor, but a good way to deal with a tiling section in the middle of a prop for example.