@dansup: FWIW, modern USB C is fast enough that a fairly cheap external USB 3 stick can serve as an effective extension of a Macbook's storage capacity. (It can also do Thunderbolt, but external Thunderbolt storage devices of good capacity are currently so expensive that upgrading the laptop actually makes sense.)

I do development on a similar model to yours, and the main thing that I sometimes feel I should upgrade it for is, 8GiB of RAM is getting a bit small. When I'll upgrade, I'll put most of my moneypoints into more RAM, not more storage.