number of textures/splat maps

I understand 4 textures per splat map, you could theoretically have as many textures as your comp can handle in memory, but any educated guess on what is considered a normal amount? I mean 4 textures by itself seems to be too little to me, roads, grass, beach, rock, maybe even some detail textures somewhere. But i'm not certain what's considered the normal amount and average computer can handle.