I have two accounts that are ~10 years old. I started churning in October (newb here!) and have opened 2 personal CC, plus the Ink. I also opened the HELOC about 3 months ago.

Chase gave me a pretty big line on the CSP and Citi gave me a big line as well. So yeah, I have some old accounts, but a lot of my available credit is because I decided to give churning a go, and they seemed to like me (at first at least).