Something I have learned:
The thought — ‘I will just “invest” in this one really great camera, this really great lens and own it forever’ is an un-true notion.
For example, a thought I had in the past:
If I just had a Leica M9 and a Leica 35mm Summilux/Summicron lens, I will stay with this system forever, and achieve ‘camera zen’, and be happy and photographically productive forever.
And this is a huge problem — with almost every single new digital camera — no matter how great, expensive, etc it is … it will sooner or later break, get outdated, get old/boring, etc.