All it takes is one new discovery to turn every theory we know on it's head. We know what we know based on constants, but if one of those constants were to be found 'off' by just a couple decimal points, or if there was an influence we simply haven't discovered yet, it would change the timing immensely. Everything we can see is old news anyway, right? Like we have no real time information of what's truly going on way past our galaxy, rather we're looking millions of years into the past. It's like trying to predict tomorrows weather in the UK based on earthquakes in Antartica in the 1800s. Or a better example would be trying to predict the first ice age after discovering snow for the first time. I personally think we are still in the baby steps of discovery which makes everything possible since we don't even know even 1% yet. Revisit this post in just 75 short years if any of us are still around. We're either going to be laughing at our naivety, or amazed that we got so close with so very VERY little data.