I agree and have experienced that too. Even without obsoleted parts, stuff will be impossible to find all the sudden, particularly specialty components. Heck, I've had vendors who simply had fabs that caught fire... but I always have a laundry list of substitutes that are pin compatible when humanly possible, which is for almost all the parts on the board. For the ones that aren't possible, that's a much smaller BOM to buy ahead of time if you absolutely have to keep the PCB design the same.

The caveat is that because MCUs are not standardized you frequently get screwed over so my replacement part list is a collection of versions of the part with different amounts of memory that are designed to be pin-compatible. Sometimes that isn't enough, and often companies aren't big enough to negotiate a guaranteed supply. But if you're not big enough to negotiate a guaranteed supply you just have to deal with buying enough of the parts to keep you in business long enough to create a new revision before you literally run out of stuff to sell...

I sympathize with the other comment berating me at length for being flippant about this, and am genuinely sorry for being flippant especially in light of their experience with the opposite issue (buying stuff and getting screwed by customers canceling orders). But I was talking about a dog washing startup. A dog washing startup vocally complaining to the news about needing to respin one board because of a supply chain interruption.

Yes, there is FCC and other testing you have to do if you significantly modify a board, so I'm not sitting here oblivious to the challenges involved in a respin. My response was to them being a poster child for the people suffering from this issue. Those of you who cannot find any component that will do the job have my absolute sympathy and I apologize for not being more verbose.