As a Baltimore guy, I fear the day the day when Ray hangs up his cleats. So I plotted his performance by year (since 2000 for regular season games) in terms of +WPA per game, +EPA per game, and Success Count (SC) per game, expecting to find some sort of noticeable decline. And that's exactly not what I found.
The graph is plotted on 2 different axes. The red line is +EPA/G and the green line is SC/G, both of which are plotted with the primary (left) vertical axis. The blue line is +WPA/G and is plotted on the secondary (right) axis.
If the graph ended at 2005, you'd think that Lewis was in the twilight of his career, but he's been making plays at a very high level since. He peaked somewhere between '01 and '03, but there's been no lasting decline to speak of.
Additionally, aside from Lewis' consistency, the fact that +EPA/G and SC/G appear to move in lockstep suggests each 'success' play may be roughly equivalent to about 0.7 net points.