Agreed on the sizing/pricing..
If you KNOW what you like...get the "value" size, but for most folks starting out... A litre is a big investment especially if they are only "dabbling" in DIY.
I spent more buying 100ml /120ml samples, trying things out, but in the end, I used it all up and repurchased based on value and taste. (and NO glass bottles).
From a storage perspective, a factory sealed 120ml is manageable in the freezer. Most folks that buy in full litres will decant a working solution of 50-100ml and leave the remainder in the deep freeze. ( I use the empty 100/120 bottles when I break down a litre)
Use wise, 120ml of base should last an average user about a year, give or take, even stored at room temperature, little to no degradation should be noticed. ( I keep my working bottle in the fridge in an opaque tupperware).
Have fun
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You said...
"Most folks that buy in full litres will decant a working solution of 50-100ml and leave the remainder in the deep freeze."
I disagree on that,
if you are suggesting that a small amount is decanted out of a liter bottle, which is then returned to the freezer now partially filled. Most people here DO NOT allow their long term storage freezer bottles to have any more than a bare minimum of air (I fill my bottles to within 1/4" of the very top because it does not expand at all or actually freeze). Also, each time nic is removed from the freezer it is subject to absorbing moisture due to the temp differences. The bottle should be allowed to come up to room temps naturally before opening.
The idea is that air contains oxygen and it is oxygen that oxidizes nic. Regardless of the rate of oxidation or the real world effect, it is surely a good idea to minimize air in the long term storage bottles. The method I outlined above requires a minimal number of bottles and results in only a couple of pours at most throughout the life of the long term storage.
I think it is a good idea for everyone to calculate their nic usage, in terms of milligrams per day, and work that into the bottle sizes they use and the amount of nic they store. A 100mg liter contains 100,000 milligrams of nic. Using me, for example, I vape about 10-12ml per day, mostly 3mg but I also use 6mg when I am out and about and may need to sneak vapes.
So I use about 50mg/day max, which results in 100,000/50 = 2000 day supply, or about a 5.5 year supply. I use about 0.5ml of concentrate per day on average, so a 30ml bottle lasts me 2 months, which is a comfortable amount for me to keep on the shelf. If I vaped 12mg, in the same amounts, that would only be a couple of week supply and I might use larger bottles for working storage.
I'm not arguing with your use of 100ml working bottles, just saying that is more than I want to keep at room temps, with a lot of air in the bottle. I don't know what the magic number of days is, but 2 months keeps me from having to think about it

. I'm just explaining the math behind my own decision. Everyone should come to their own conclusion on this since we have little firm data, except that less air in the bottle is better, and lower temps (preferably a freezer) are better. And I have multiple liters because I want to be prepared for either no availability at all, or very high taxes on it, and I think that will come sooner than later and I don't want to be in the mad dash when new regs or taxes are announced and imminent. So I have a 10+ year time horizon on this.
There is also a safety issue here. Since the working bottle is handled often, it is more subject to breakage. Now, you have to decide about how you feel about 100ml vs 30ml of nic splattering all over your kitchen or other working area. Plus, larger bottles are probably more fragile than smaller bottles. I particularly worry about that in regards to freezer storage of some larger bottles but those bottles are all wrapped inside heavy duty zip lock freezer bags so hopefully that would contain a broken bottle spill.