Hi Ben, I'm at two years and still get a bit of soreness in my right hip when I sit too much.
Exercise definitely keeps me loose and overall makes me feel better. I can tell the difference since I work on a computer all day; when things get intense at work, I can be sitting in one spot for hours. I don't really get startup pain anymore, but do get a bit sore when I've sat in one position for way too long.
Have your X-Rays been pretty good since the operation? If so, I notice you don't run, but maybe, since you get good results from exercise, going to a physical therapist to strengthen the area may help.
I think for me, I need to keep up the exercise to recover correctly, even then. In my case, I had seven years of OA, with possible atrophy of muscles, back body mechanics building up, etc. so I would expect some issues to last a while, something that needs work long term.
I would also talk to your surgeon, tell them how you feel and eliminate the device as an issue - then you can take care of muscular issues if they are there.
As to longevity, we are at the first (statistical) wave of adopters, so we are setting the standards. There are plenty of people who are successful at 10 years (see the national registries), and stories here about some really early HRs who are doing fine with theirs in 20 years.
My own opinion (and hope) is that I'll actually be able to take my metal HRs with me when I go and trip the metal detectors at the pearly gates.