The standard practice is to either make up the concentrate from its powder form (D76/ID11) or to buy in the liquid concentrate (HC110/Rodinal) - then keep this concentrate in a bottle/container in the presence of as little oxygen as you can manage (squashed the bottle/insert inert gas in the air pocket/glass beads - are all standard tricks to exclude oxygen)
This bottle of concentrate should then be kept in a cool dark place.
When you have films to develop, you take some of this concentrate and dilute it to the required working solution immediately before you use it.
The bottle of concentrate is then further squashed/refilled with inert gas/has more glass beads added/what ever else - to again exclude as much oxygen as possible from the storage bottle.
Chemicals such as ID11/D76 in dry powder form have a huge shelf life.
ID11/D76 in concentrate form have a shelf life of easily 6 months
ID11/D76 is THE standard developer against which all other developers are compared
D76 is Kodaks version of the standard developer/ ID11 is Ilfords version
Personally, I make up packs 5L of ID11 and if I don't intend to use it all straight away I decant into 500ml bottles - 500ml happens to be the amount of Dev I need to process a tank of film
While ID11 doesn't have the shelf life of Rodinal, it is a much more straight forward developer to use (no need to pre-soak).
As ever with these things there is no one clear answer (otherwise we would all be using it) but a matter of personal taste.