Yes, they do come down eventually, I only said they are the hardest to get under control - but not impossible as you say. Also, I do check now and again as I said, but for a new person with limited supplies of strips I believe it's more useful for them to use their strips working out what they can and can't eat which can give comparitively rapid improvements.
For guestimating HbA1c, I personally don't think they're much help. I keep a graph of all my post prandial readings, and my occasional before bed and fasting BGs, work out a true average allowing for peaks and flat lines etc, and use one of the formulas available to get a guesstimate. Last test, I guessed 5.5% and got 5.7% so not too bad.