Yes, I believe the steady levels are best but what if they are slightly higher than NICE guidelines? I was just thinking - over the past couple of days my levels were swinging from 4.7- over 8 and I felt rotten usually they are pretty steady at 4.5-5.5 usually lowest after exercise and hovering around 5 before and after meals and I feel really well. My friend has steady levels around 7-9 and he says he feels fine on this. But I thought damage could start at 7.8 and over? I asked this question out of just curiosity really.
For me, my endeavour is to keep my levels within the non-diabetic ranges, and thus far, my body is able to cope with that, with my chosen lifestyle. If that became impossible, for whatever reason, I'd, personally, want them as low, and steady, as I could maintain, again within my chosen lifestyle.
People are all different in terms of how their body copes with what life throws at it, and also the individual's chosen way of eating. Not everyone is willing to give up, say, bread or crisps, and whilst I'm fine pretty much living without either of those, not everybody is.
The future is a gamble. My gamble is that I carry on as I'm doing now, when perhaps I could relax things a bit more and still have decent enough scores. Someone else may elect to gamble eating a wider range of foods, involving some things I choose not to bother with, in order to have, for them, a "better", more normalised life today, gambling their body will continue to cope with the choices over a longer term.
Finally, feeling "fine" is all very subjective. One man's (or woman's) "fine" is another's "dragging myself along". "Fine" is where I measure my personal "normal". Feeling fine is where most people decribe their ticking over state. How many people have we seen arrive here "feeling fine", then some weeks later they "feel so much better, with more energy, better sleeping" or whatever?
I'm not suggesting for a moment your friend is unwell or being economical with the truth in terms of how he feels, just saying it's based on how he usually feels, doing what he usually does. He might feel better or worse if he tweaked his lifestyle. Who knows.