Hoping what they don't tell you is that you don't necessarily lose your sight completely - it's not like being in pitch dark. There's swirly blood in your vision, but as you move your eye around it moves too, and it's often possible to either kind of look out of the corner of your eye (peripheral vision), or look one way then back in the other direction quickly, it takes a moment for the blood to swirl back into view so you can see for a bit.
I was 29 when I first had a bleed (in one eye, which cleared all by itself), and I was 36 when I had the 2nd vitrectomy. It's more to do with how long you've had diabetes - I was dx in 1984 so a fair while! Rapid changes in HbA1c are one of the biggest risk factors - even if that change is an improvement. Eyes like the status quo, they're not fans of change.
Will be back in a bit, got a preschool run to do now! :o