Just as I suspected, in the case of my grandpa sweater, the tubular bind-off at the Lower Edge and front bands, did not hold up well with wear and stretched to much out of shape. So much so, that I decided to take the drastic step and frog back the collar bands and the lower edge ribbing. It took a significant bit of resolve to take off all the buttons and rip out all the buttonholes reinforced with hand-sewing, but it needed to be done, if this cardigan were to make my frequently worn list.
I redid the ribbings with smaller-sized needle and did regular bind-off in rib. I lost some yarn in frogging and decided to forgo the shawl collar, considering the little extra yarn that I had, was used up in the lower edge ribbing.  It was all worth it in the end, as the regular bind-off is much more stable and I do not miss the shawl collar much.