

It is a somewhat old-fashioned choice these days, but Arctic Silver 5 paste is still my go-to. It is very thick and not prone to pump-out or dry-out. I have systems that I have taken apart where the paste was still tacky a good 5-6 years later. I think some modern pastes are a degree or two cooler, but for a 15W U-series CPU I do not think that is as much of a concern.
Most tutorials online will be for desktop CPUs and will tell you to put a pea-sized bead in the center and press down, but this is more suitable for desktop CPUs with an integrated heat spreader and not laptop CPUs, which are typically direct die application and would probably either leave a ton of excess paste from a pea-sized dot, or risk an exposed corner for a smaller dot.
For direct die, I would suggest spreading an even layer of paste from edge to edge of the die using the edge of an old credit card or the like. You want to avoid stirring up the paste too much in order to avoid introducing air bubbles which could cause localized hot spots on the die.
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.