The lifespan of stars varies a lot by type and size, with largest stars having a very short life-span of maybe a few dozen million of years and small ones up to dozens of billions of years. I'm not sure what the average is.

> A star "lasts" about 10 billion years, so you'd expect about 1 in 10 billion stars to 'die' each year, but only a tiny proportion (the very largest) go supernova.

This analysis really doesn't work. Star lifespan is inversely correlated to size. A star large enough to just barely go supernova is only going to live for ~100M years, and as they get bigger, the lifespans fall rapidly.

(Why? Because gravity is what provides the pressure for fusion to happen, and so more gravity means fusion happens faster. For large stars, the luminosity is something like the mass to the 3.5th power. Also, convection works less well for larger stars, so as stars grow bigger, ever smaller proportion of the star takes any part in the fusion reactions in the core.)

So only 0.12% of all main sequence stars, have the mass that can become the most common type of supernova, and they apparently only last for about 100 million years.

Wouldn’t the creation dates of stars be clustered around certain points in time. So the supernovas should also happen in groups?

what's the rate of Type Ia supernovas? Higher I would guess? (n>=2-aries are common and medium mass main sequence stars are common, though it takes them a while to get to white dwarf)