It doesn’t matter, and is indeed essential the more details you add to a way. When a speed limit changes, or the number of lanes changes, or the est_width or width change then if you are tagging such details you will need to split the way.

I believe some people have been using route relations to define the complete way, although I don’t think this is currently necessary for anything if the individual sections are all correctly tagged (although I guess it makes maintenance easier if you only have the name and ref tags on the relation and not on all the sections, I think it will be more confusing in the way existing editors handle relations).