I've just finished building a home made box camera with which I want to travel around China taking picures or people I like for pleasure, and of tourist to make a living. I wanted to use Rodinal because it lasts for a very long time and it's very easy to use, but only found Dektol in the store and I have never used it.
My problem is that travelling with 5l of stock solution is not an option, I have not found any information about if I can mix only a small portion of the pouder and then close carefully the rest. The only similar information I found is a very categorical "mix immediately after opening" in Ilford's website concerning one of Ilford's pouders, but I don't know if it is the same for any pouder or if they might exagerate a little.
Any of you have tried not to mix all the pouder imediately but doing so after some months?

Thank you very much!