If you aren't having a problem, it should be fine. The memory controller on the CPU is only guaranteed to work with DDR4-3200, but if you can get higher speeds to work, that's good. It's a form of overclocking, just like the overclock you did for the core frequency.
Since the RAM is rated for that, the RAM itself should be able to run at that speed indefinitely. The memory controller on the CPU might have difficulty years down the road if the silicon degrades, but that's not a guarantee. Especially since you're willing to run it with an overclock, I don't see why that would be a concern for you.