Just to be clear those are the rudimentarily intelligent (which assume to mean stereotypically cave-man like)conical creatures that the Great Race of Yith transferred their minds to to escape the destruction of their homeworld (Yith). The concial thing's original minds ended up in the old bodies of the race of Yith.
The conical creatures had previously been raised and herded as food by the Flying Polyps. The Yith arrived and having great technological proficiency changed they built weapons and fought a war against the polyps in their new conical bodies and drove the polyps under ground into deep subterranean basalt chambers where they stayed for a long time and possibly built cities there.
Eventually the polyps broke out and wiped out the conical creatures but by then the Great race had transferred their minds to beetle like creatures that exist on Earth after the extinction of man. Presumably the polyps either die out, leave, or return underground after their victory. Perhaps having wiped out the conical beings they lose a primary food source and so have no reason to stay.
Either way, during the age of man the conical creatures and the polyps aren't around, the elder things are either extinct or hiding in a degraded state in the oceans following a shoggoth rebellion and an ice age drove them off the land, and the star spawn are asleep along with C'thulhu in the sunken city of R'lyeh. The many tentacled things that Yog Sothoth was keen to let back into your world via the Watley family are locked away in some other dimension lusting for the time they can return and subjugate or destroy mankind.
Of course we know they fail because in the Shadow out of Time Peasely, transfered to one of the conical creatures, meets people from the distant future including Nug-Soth from 16,000 AD.
So man lasts at least that long.
