I'm one of those who "would never grow old in this system of things". I was promised that back in 1969-right! I was 22 then and now I'm a few months short of 70!
That being said, my wife and I along with many, many of our long time jw friends and family have "grown old in this system". That means that we all visit the doctors offices much, much more these days. Many of these doctors visits require us to have a blood test done prior to our appointments.
This is where I reverse "witness at every opportunity"! Every time I hear someone say that they are going in to have a blood test, I say,
"Oh, your going to have to violate god's law regarding the sanctity of blood you know"
Or when my wife or I have to go have blood drawn, I remind her: "Well let's go violate god's law on blood today."
Needless to say, my "witnessing" in not well received but as we are so often reminded, sometimes "the truth hurts".