> 2 years

I've been thinking about this a lot. 2~3 years is a long time, long enough to have a pretty good grasp on what a code maintained by 50~100 does in pretty concrete terms, come up with decent improvement ideas, and see at least one or two structural ideas hit production.

If the person then stays 1 or 2 more years they get a chance to further refine, but usually will be moved up the ladder Peter Principle style. If they get a chance to lead these architecture changes that company has a chance to be on a decent path technally speaking.

I'm totally with you on the gist of it: architects will usually be a central switch arranging these ideas coming from more knowledgeable places. In the best terms I see their role as guaranteeing consistency and making sure teams don't impede each other's designs.