Why be concerned? Buy the 5 liter kit and enjoy all the developer you can use. If it gets old, dispose of it and mix up a new batch. Shoot all the film you want! For the next 2 months or so (you pick the time period) you have all the developer you can use for $8.00(posted 8220 days ago)What I do is make the 5 liters, divide it into 1 liter, 500ml, and 125ml bottles. All brown glass, quite full and tightly capped. When the smallest bottles are used up I transfer the contents from the larger ones to the smaller ones. So I have 125ml premeasured bottles to work from that are always as fresh as possible. If I think its getting old I just dump it and make a new batch.
Why 125ml? Because I can simply mix it with 125ml of water for 250ml of 1:1 or 250ml water for 1:2 or 375ml water for 1:3. Want 500ml of 1:1? Use 2 125ml bottles. Simple, fast and always as fresh as it can be.