Google's John Mueller explained in a webmaster video at the 54:51 mark that long term noindex, follow commands will eventually equate to a noindex, nofollow directive as well. Why, well, eventually Google will stop going to the page because of the noindex, remove it from the index, and thus not be able to follow the links on that page.
I didn't know this was something SEOs didn't realize to be honest. But it seems something SEOs are chattering about both at WebmasterWorld and Twitter.
Here is the video embed:
Here is the transcript:
So it's kind of tricky with noindex. Which which I think is something somewhat of a misconception in general with a the SEO community. In that with a noindex and follow it's still the case that we see the noindex. Snd in the first step we say okay you don't want this page shown in the search results. We'll still keep it in our index, we just won't show it and then we can follow those links.How long does it take for a noindex, follow to be treated like a noindex, nofollow? John Mueller later on said "it depends," and of course it depends on crawl frequency and some other factors.
But if we see the noindex there for longer than we think this this page really doesn't want to be used in search so we will remove it completely. And then we won't follow the links anyway. So in noindex and follow is essentially kind of the same as a noindex, nofollow. There's no really big difference there in the long run.
Forum discussion at WebmasterWorld and Twitter.It depends :-).— John â.o(â§â-½â¦)o.â (@JohnMu) December 27, 2017
You probably knew that already :-))