Software pain points for long-term equipment

The other bit of pain that shows up again and again is that hardware is relatively simple stuff in an extremely complex environment; we exploit the relatively simple environment software faces (since it's a virtual world created by the hardware) to allow us to spend our thinking budget on making the software much more complex.

This shows up when you're trying to replace a 1990s product - your total hardware design is an order of magnitude smaller as digital files (schematics, PCB layouts, drilling decisions, component choices etc) than the software source code, even when both are compressed with state of the art compressors. And that drives a new problem - we don't build anything completely in isolation, and even if you retained the source for your part of the software, there's a good chance that you bought something in and didn't retain source code. For example, there's systems out there built on top of Windows Embedded - and if the part you need to fix is in the Windows Embedded layer, you're not going to have source, and it'll cost a lot, too.