I subject my self to boxed wine, so I have lots of leftovers for developer. It keeps very well in them. Years, IME, because there is no air contact if you squeeze out the air after filling. Nice and compact and built-in spout too. You can't pour back in for replenishing, so I only use them for paper developer now.
You can fill them, but not pour back? Could you explain on that.
You have to take the inner bag out of the cardboard box, tip them up, yank the spout out, and pour the liquid in without spilling anything, and then squeeze the air back out. It's not terribly difficult but it's too inconvenient to do this every time you develop. It's better to use a bottle or something. It's fine for chemicals that you just fill it up and then use all up.