Hi Muttley, I hear what you are saying about the running RSI.
I run 3x a week averaging about 20miles a week. I also cycle 3x for an average of about 30miles a week.
I decided to try base training after a season of hard training and too many coughs, colds & chest infections. I had to slow down from doing what I thought were easy 10m/m to almost 14m/m but I am now doing 11m/m at 65% WHR so I know it is working for me.
I am not planning on doing it for too long, maybe 10wks in total, but figured if I got a good aerobic base before starting my normal training of 4x a week with one speedwork, one tempo, one recovery and one long it may help me reduce the chance of illness as I think I was seriously overtraining before as I wasn't aware how hard I was training every session.