Congrats on the new hip! Mine was replaced at age 50 and I had also been a runner, but never marathons. Anyway, along with PT I was recommended to walk easy ground (around town) at ~2-3 weeks post op. Started easy gym workouts by 2 months, and did a weekend cross-country backpacking trip over very rocky ground with a ~30lb pack at 3 months (with doc’s OK), and skiing moderate terrain by 4 months (he emphasized “moderate”). He said full recovery would be ~18 months for the joint capsule to heal, bones to recover, nerve issues to cease, etc. Also you will be working on fixing goofy patterns and imbalances that you picked up while dealing with a wonky hip. I’m still working on that, 3+ years later.
I was not given an official date for re-starting running but I remember thinking that running sounded completely unappealing to me until I hit the 6 month mark, which was when it started to seem appealing, and I started to ease back in. Figured I’d listen to that little voice tell me when it was OK to re-start. I have gained back all of my speed and endurance (actually I’m faster now ‘cos I’d been persisting in running with the bad hip, I was slow and in pain all the time). I run only trails, and they are usually steep and rocky to some degree.
In short, everyone is different, and don’t rush it–listen to your body and let things heal, you’ll be glad you did! We all want to get back to the stuff we did before, but this is a major operation and it needs time. Good luck!