Toneing with coffee and tea seems to me just coloring the paper base and not really affecting the image tone by much. May as well soak the picture in Easter egg dye....
Well, yes, but it can be done to great effect when done with the right image / subject matter.

I wouldn't use it on prints where archivalness (is that a word?) is critical. Although coffee / tea / red wine can be fun to play with, they are far from archival.

(yep, red wine. Love the effect.)