Running injury free for 5 Months

I've been running injury free for nearly 5 months now. Ok, I had a bit of a calf strain recently, so I took a week off. But other than that the body has held out. I've done some longer runs from time to time (+20km) and all was good.

What do I put this down to? These are my injury prevention rules:

1. Run with a bus ticket. When I don't feel good, like a niggle that gradually gets worse, I just stop and walk or take a bus home.
2. Recovery time. I run every second or third day. I'm not commuting daily any more, so I get adequate time to recover.
3. Sufficient warm-up. Get the knees, calves, glutes, ankles and feet properly warmed up.
4. Calf socks - since most of my problems are with the lower legs, I always run with calf socks. I don't know if they really help, but since I've been using then I've had no issues.
5. Focus on running form. Short stride, landing under the body, "claw-back" etc. There are many sources online - chi-running, pose method and these.