I did sterilize my bottles especially when new the same way you sterilize jars for canning, removed the wire part, boiled and dried.
I do the same. Might be over-fussy, but I buy large quantities of distilled water to boil my glassware up in (I buy it online from Lubrisolve, alomg with bottles of their VG , and other bits and pieces). If you boill in tap- water , you can actually see the mineral deposits on the bottles when you fish them out. I don't know if they would re-dissolve in the nic base, but I'd rather not risk it.
As for putting metal vessels in the freezer, that isn't done, the reason being that metals have a high coefficient of thermal expansion, and will therefore shrink, to a significant degree, at low temperatures. I would suggest that you don't want your container, nor even just your lid, deforming too much
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I've noticed two or three nic base manufacturers offering "freezer packs" . These consisted in a set s 250 ml or 500 ml glass bottles ( containinng nic -base, ofc) with plastic lids. One site cautioned against "freezing" larger bottles (more than 500ml, IIRC)
I put "freezing!" in quotes because nic base doesn't actually freeze normal freezer temperatures, it just gets "thicker" and is unworkable until you warm it up again.
Conversely water does freeze. as we all know, and it also does this highly unusual thing of expanding upon freezing . That's the reason why you shouild never freeze aqueous products in glass. The bottle will explode. I mention this because this might perhaps be a problem wirth "aqueous glycerine", and other modifications you (or the supplier) might want to make to the nic liquid in advance. An exploded bottle of nic base would be one heck of a health hazzard, I should think.
(edited for multiple typos, as usual)