Is it realistic to run a loop completely passively during light loads, or is it dangerous?

Recently, my pump died on me. No big deal, nothing happened, I just switched it out with a new one. The funny thing though, is that it took me a whole week to even *notice* it was off.

During that week, I'd been doing nothing but very light workloads that barely solicited the CPU and GPU. Temps never even got near throttle levels even with the pump being off during that time. Although I did notice they were higher than normal at some point, I didn't think much of it.

Then, comes the weekend, and I launch a game. I was able to game for a whole hour before the GPU temp became too hot and the whole thing shut down on me, which made me notice that the pump was indeed off, and (according to my temperature logs) had been off for a while.

So, here's my question: is it viable at all to turn off the whole loop on purpose when the workload is light? It seems to me that I could have gone much longer without ever seeing any issue arise, as apparently stagnant water is enough to dissipate heat passively. I could just set up my pump to turn on only when the coolant and/or the components start to heat up significantly.

Am I mistaken? Is there a risk in doing this I haven't thought about? The idea of a completely silent PC when I'm not rendering or playing sounds very appealing to me.