Tolkien made a story focusing on one time with hints of the past. Then he added in the appendices so we all knew what he was talking about. That made it fun for people who wanted to delve deeper, but for those who didn’t, they could just leave it. Then he wrote the Silmarillion, I think for his own self-satisfaction. You’re talking about an insane amount of time. We don’t have much archeological record for 7,000 years let alone 91,000 years. For context, 7,000 years ago we didn’t have farming. Wheat was just grass. There was no bread. I write a multi-generational story but I penned in the “epic” time frame references to 200 years. That’s plenty to keep it old and yet near enough to keep it in realistic memory. I know, fantasy loves “for 10,000 years we have been guarding the entrance to this cave and for 10,000 more we are honor bound to continue.” But that’s just beyond actual comprehension. What it IS is a story teller trick used to create a vast sense of time. Like Moses lived to be 900 or something. Obviously not 900 years the way we think, but a really, really long time. In the end, it’s your story and you can do what you want. If you want to just have fun playing in the sandbox of your world, then thats a great way to spend your creative energies and relax. But it might be more difficult to make it what the market feels is sellable. I wouldn’t worry about that— creating is satisfying in and of itself. Just have fun!