Lol, my first iPad was a 32GB iPad 2 (preordered) thinking it would be adequate for my needs. Filled it up the same weekend I received it and I ended up ordering the 64GB iPad 2 (backordered 1-2 months already, I think?). I didn't want to go without an iPad that long so I ended up giving the 32GB to my mom when I finally got my 64GB. Even then, 64GB stopped being enough for me even before the 128GB iPad 4 was released. I couldn't update my apps on the 64GB iPad 3 because I didn't have enough space.
I don't future proof but I know I require a lot of storage else I'll likely need to constantly manage/switch out content after just a month or so. Note, I have a 20TB NAS at home so no, I'm not trying to store all my stuff on an iPad. They won't fit. I just like having a nice selection of content available for whatever tickles my fancy (favorites and TBR/TBW pile).
I usually get top storage + LTE. Pricey, sure, but those features are what's ideal for my usage. I just upgrade when there's a feature I really, really want (which is often more storage
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). Annual depreciation is killer otherwise. For me, those two features are more important than always having the latest model.
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In fairness, you probably don't need to upgrade storage on all devices in the household. I do it on mine because I have a use for it and relying on the cloud/internet isn't a viable alternative. For the rest of household, I just get them what they need which given their usage (Facebook, video streaming, online banking, casual games) is just the base 32-64GB storage.
Even on my devices, I'm selective. I tend to max out the iPad because I know I'll need/use extra storage there. The iPhone, I can easily live with 128-256GB and can even get by on 64GB if necessary.