The purpose of starter is to add to replenisher to make working solution, whether you are using the working solution one-shot or many times. Many users on APUG have reported that they get acceptable results without adding starter to RA-4 replenisher. You can just add the starter as instructions say, or try it without and see if the results are acceptable to you.

If you store developer or replenisher in completely filled glass bottles, you can get many months, even years of life from it. High quality plastic may work as well.