I've never been comfortable with re-using any developer, except Diafine, in my darkroom. With each use, the developer loses strength and picks up byproducts of development. To compensate, you need to add development time or run a replenishment system. Neither of these methods is convenient or reliable for the home user developing small quantities of film. In a commercial lab with access to test strips, and having a relatively stable workload, running a reliable and stable replenished line makes economic sense. It does not make sense for the home user running only a few rolls of film on an erratic schedule.

For the home user, the most reliable and repeatable results are to be had by using the developer as a one shot solution. Be it full strength stock solution or diluted makes no difference. For my own work, I typically will use XTOL anywhere from full strength stock solution or diluted 1+1 to 1+3 depending on the application. At 1+1 you might get a little more apparent grain structure, but it's hardly worth mentioning unless you plan enlargements of 10x or greater. Even then, the differences are not worth squabbling about.