They call that: Paralysis by Analysis; a person talking themselves right out of doing something. Then they break it down into tiny numbers to make it seem like it is insignificant savings. It gets kind of silly because if a person saw a $20 bill on the ground, who would not pick it up? Yet, they will deduce reasons why saving $17 a month is not worth it? Really? if you found (20) $20 bills on the ground you would not pick any of them up?
My local school board does this: takes 1.5 million in potential savings, divides that number by the number of tax payers and says, saving them $15 per year does not mean anything. Really, what part of saving 1.5 million did they miss?
Your deductions are amiss because it need not be that complicated because a person can figure out how to lower their initial costs. A person does not need an expensive new tank for instance. Here in Maine you can get used 275 gallon oil tanks for almost nothing since so many people are going to mini-splits. Just tee the two tanks together and you have 550 gallons of diesel fuel in storage.
I am all set up because I have been getting that Genset set up, so I will do this.
I can see no reason why storing something a person will eventually use is a bad idea. It would be like heating with firewood and telling someone to go out and cut dead trees as they needed them instead of having a year or two of firewood in storage.