About the toning part: A sulfide toner using bleach will tone less the darker the print is, because it is a 'top down' type of developer that is most intense in the highlights. That's not necessarily a quality of the toner itself, but that's how the bleach works; the highlights bleach out first.
Therefore, if you want similar toning effect in a darker print with few highlights, you must bleach it longer than a lighter print.
Selenium, on the other hand, is a 'bottom up' type of toner, which works to convert the developed silver to silver selenide, and is most effective in the areas of a print that has the most silver density, so it starts to show visible change in the shadows first. Leave the print in for enough time, and eventually the print will be toned to completion, though.
Those are the toning variables.
Regarding print development, I used to use 2 minutes for 8x10 prints, 2m30s for 11x14, and 3m for 16x20, but have changed to 2m30s for 8x10, 3m20s for 11x14, and 4m for 16x20. I find that the extra time helps compensate for a move to a larger size print. But why I use constant times is simply because it's easier for me to get what I want that way. It also helps me identify if there is a problem with my paper.
I use replenished Ethol LPD, which has the approximate working strength of LPD 1+2, but obviously the left over bromides and such act as restrainers, so the behavior and tonality is a little different. Shadows are a bit more open, and the highlights take on this really beautiful radiance that I love.
The nice thing about replenished LPD is that it never goes weak, if replenished properly. It maintains its activity, and goes and goes and goes. The energizer bunny comes to mind.
(I still haven't tried using your trick with super strength lith developer, but some day I will).