Were you replacing just the 4 year of PG or do you replace you Nic around the 4 year mark too?
I stocked up during the last scare 2015-2016 out of need. Then it all went away for years and now its back. This was my first attempt at long storage. Like everyone else I wouldn't be stocking up now accept for the rules coming down the pike.
It so happened that all my supplies lasted until now. Still have my five major flavor concentrate left that am using still. Menthol 120ml, Ry4 Double 600 ml, Vanillin 30ml, Commercial tobacco 64 ml and candy cotton 120 ml.
Not worried with concentrates I make my own from tea's with some PG or VG. Same with tobacco. Just the concentrates make it easier and less messy.\
The only thing am concerned with is the Nic IMO: think like last time there was a run on it. Might even be hard to get one day years from today. Going to be a big demand all these vaping supply shops that sell Nic will be gone and when that happens the price will go sky high.