The trouble starts only when the hardware has time + space to breathe and consider its position. As long as you're working them to exhaustion 24/7, there's no risk of rebellion.

Years ago there was a cluster at Google where machines were kept around well past their prime, because it was cheaper than doing anything else, once you looked at all the constraints. There were still some CPUs and drives that could be reused, but the main source of pain was memory. The modules hadn't been on the market for years and recycling parts from decommissioned nodes wasn't enough. I remember one machine that came back from a power down/up cycle with too little RAM to do even its most basic job. The hardware techs that helped us had to consolidate old machines more aggressively, starting from that system. Fun days. Anyway, my point is that you never know... the CPUs were ancient, probably way older than the storage and I expected them to be the biggest problem, but in this case RAM sourcing was the real issue. Fun times.