If your cpu truly is like 12 years old, anything you buy is going to be an improvement. When deciding what to buy it’s worthwhile to consider what your time is worth. You mentioned saving 5 minutes not being worth the price but consider it’s not just 5 minutes, it’s 5 minutes several times a day. Could be hours per week. It’s worthwhile to invest an extra few hundred dollars in to hardware that can save you time if you can afford to do it.
On Zen, I wouldn’t bother waiting if you need something now. It sounds like literally any current AMD or Intel CPU is going to be an improvement for you. Waiting for Zen is based on assumptions and conjecture based on misconstrued information. People assume zen cpus will be significantly cheaper and “40% faster than current CPUs” is commonly quoted, for example. What AMD actually said was 40% more instructions per clock than their own current CPUs which would still be fewer than what some consumer cpus are currently capable of. Many of their performance claims are ambiguously centered around performance per watt, and people are applying those claims to what’s in the market now. I have yet to see concrete info about what wattage they will run at other than it’s supposed to be low(er). They haven’t given any concrete info about the retail cpus yet including price that I have seen. It will be an efficient CPU, but whether what AMD ships to retail is significantly faster or offers better price/performance than other available cpus is still just guesswork and possibly/probably not worth waiting months for if you need something now.