Skip, good to hear it is working out well, and that you found the manuals link. Developer does tend to darken, I think, mine definitely does to some extent. Nothing much to worry about as long as it is still working well I'd say. I use that same replenishment setting on my cp31 setup as well. It is pretty frugal with chemistry, when set like that. Definitely a nice thing from a cost perspective.
If you can align your enlarger well enough that you can have the corners sharp at f5.6 or close to wide open, that will help extend tube life. For medium format I was exposing at f/8, but with laser alignment, I think I can print sharp prints now at 5.6 or 6, hopefully.
Are you printing 35mm only? If so, get and use the 35mm mixing chamber, it concentrates the light more, saves tube life, and brighter focusing, etc. I have at least 2 of those, if you need one.