Precisely. In my experience, even if you can upgrade the GPU or CPU (really only Clevos let you do this), it's far from cost efficient. Might as well just buy next gen laptop when the time comes than upgrading an MXM GPU since they're generally expensive and hard to find. I think across the probably 15 Clevos I've had, I decided that upgrading the GPU was worth it a single time: I moved from the the unspeakably awful 480m to a 485m. And even then I might have well just waited a few months to buy a new barebones with a better CPU since the GPU was so pricey.Like Harmattan said, you probably won't get official hints of repairability.
To expand on that: be realistic about what you can upgrade. Don't expect to replace the CPU or GPU. Even if you can, you may be unwittingly introducing thermal or power issues as you ask the cooling system to handle chips it was never designed for. I've seen more than a few people who were wildly optimistic about keeping a laptop relevant for several years... only to realize that they either couldn't upgrade it enough to make that happen, or the expenses and hassles necessary weren't worthwhile (say, hunting down some pricey GPU module that would work with their PC).
It's part of why I don't mind buying MacBooks despite the lack of upgradeability. You do need to anticipate your needs years ahead of time, but you probably weren't going to do much to upgrade it anyway — you might as well spend some money up front and relax.