"But I don't understand the rest of your observation:

and there isn't as much time for tax free growth"

Well, that included "once you are over 70"...

"Regardless of the time period, the end result is going to be the same"

Yep; you're dead, and someone else deals with any residual funds. But, you're either dead sooner, or you're dead later.

If I am converting to maximize tax free growth and earnings, I would rather do so while I have a more statistical probability that paying tax on the conversion will be recouped in growth. And hope I don't die until 5 years after that latest conversion to Roth.