I make an 8 drop solution diluted to 120 ml for him for the day since he is taking less than 1 drop each time, but I make it fresh each time for myself since I take 2 drops each time. My understanding is that it is better to make it fresh each time, but I am ok with taking it slow with Drake, since he has so many partially known but uncertain issues. Don't get me started on the vets, but I don't want to over-do this and have to bring him in for more misdiagnoses and trial & error meds that do more harm than good.
If I were in your shoes with a known cancer, I would probably be more aggressive and make it fresh each time.