My criteria for when to upgrade is simple: when it no longer runs the games I want to play at an acceptable framerate. I have a 30-series card, but I have yet to play a game where I had a problem with framerate, so I have no plans to upgrade. It wasn’t until I ran into a game where I was getting 20 FPS at minimum settings on my old GTX 960 that I decided it was time to upgrade.

One could probably say the same about workstation performance if it is taking too long to run and becoming a productivity bottleneck. For something like that, I think it comes down to an assessment of how much you will be spending versus what percentage reduction in processing time you will see out of the upgrade. If it is only a marginal improvement, maybe wait, but if it would be a substantial uplift, then it is probably a worthwhile return on investment.

Depending on what your definition of “decent” is, I think you may be disappointed. The cutoff for support is around 8th gen intel and AMD 3000-series from circa 2017-2018. Even my old 2017 laptop with a quad-core i5-8250U is supported.

Unless there are specific recent CPU models which are not supported, I think the majority of the unsupported laptops are going to be decade-old 6th and 7th gen or 1000/2000-series machines. These machines already go for fairly low prices on the used market.