Oldest component is my secondary monitor, an LG IPS231. Got it as a gift for christmas one year. Couldn't tell you when, but the model is from 2011. Everything else is mid 2018 or newer when I built this system. Went all M.2 for storage so no carrying over hard drives. Swapped to SFF, so I needed an SFX power supply, SFF case, and didn't have room for a CD drive. Speakers were replaced last year, got a new mouse and headset for christmas and the keyboard is "new to me" when I grabbed an old one from storage after my other one died last year.
My old tower is still kicking around in use by my brother. It has the original case, HDD, and PSU from 2008.