Will running my PC 24/7 for mining damage it or void the warranty?

Computers are designed to run continuously - most servers, scientific workstations, and home NAS boxes do exactly that for years. The real risks for a home mining rig are heat and dust, not the uptime itself. Keep the case clean (compressed air every couple of months), make sure airflow is not blocked, and consider undervolting the GPU to drop temperatures by 10-15°C. Standard consumer warranties from major manufacturers do not list mining as a disqualifying use, though some board partners have policies about overclocking. Stock or undervolted operation is essentially indistinguishable from gaming or video editing from the hardware's perspective.