Here’s my two cents – take it for what it’s worth. I had a THR on my right hip two years ago. I was diagnosed with osteoarthritis nearly 8 years ago when I was 44. I was an ultra runner for many years. Long story short, before my surgery I made a conscious effort to alternate running with swimming, biking, and any other physical activity to mentally prepare for the change that would be inevitable. The sooner you get on board with the idea of adding swimming or biking or other low impact activities, the better off you will be mentally after your total hip replacement. Coming to terms with the idea of not running or not running as much as you used too simply takes time.
As I mentioned, I am two years post surgery, (age 52) and I am very happy with the decision I made. I still run/walk one or two times a week, swim and bike on alternate days and throw in some strength training. The idea of prematurely wearing out the hardware makes me evaluate my choices any time I head out the door.
I would encourage you to do extensive research on the pros and cons of running after THR and how it can affect your body. Keep in mind that even though the materials used now are extremely durable, there are still particles that wear off over time. That said your THR could last 30+ years or it could last 5-10 years depending on how much wear and tear you put on the device. And on top of this revisions are never that successful if you read any literature on the subject.
From my point of view, I would put it off until you know it’s time. Believe me, you will know when it’s time because it literally will be too painful doing your daily activities and keep you up at night.
Good luck with your decision!