I’m 54, started smart-trainer training a year ago. I’m 5’8", 153lb and have been back cycling for around 6 years after a long layoff but doing other sports.
I was going pretty well and was persuaded to start time trialing at 50, to which I quickly became addicted!
FTP a year ago was 242 (via TR 20 minute test) and went up to 275 by Spring 2018.
My starting FTP is now 275 (via the ramp test,) but in reality it feels more like 265-270 based on the perceived effort and heart rate at this early stage in SSB1, however, even allowing for an over-stating of this, I’d expect to be above maybe 280 by the end of the winter, which would equate to 4W/kg I think.
And I get caned by a local 68 year old time triallist who came into tt-ing in his mid sixties - a regular cyclist and ex-runner of some repute I am told.