This sentence alone is immediately countered by the word "eternity". You have no idea if there is always going to be people. It's actually a statistical certainty that "people" won't always exist. Eternity stretches beyond that.
But let's pretend that the way it works is that you live on earth for an infinite amount of time and earth is always habitable and there are always a bunch of people walking around and you are just hanging out among them throughout the ages. Even then, there is an extent to what is scientifically possible. It would take an extremely long time to learn everything, but eventually it would happen. There is a cap and eternity extends beyond that. Forever.
Again this is implying that everything goes your way and you don't eventually get trapped under a fallen building or captured for testing.