Does merging material groups make render faster?

reko34

I'm making custom figures and want to make them easy to use and resource saving. Some part of the figure use the same texture map. Leaving more material groups makes it easy to adjust color (use the same map but change the front color). But I wonder if more groups lead to more time for rendering (loading the texture file several times?).

In DAZ figures like V4 there exist such situations too, e.g. torso and nipple, leg and foot use the same material settings. Will render progress become more quickly if I merge the groups?