In 2037, the Su-30, like today's MiG-21, crashed almost every month,In an ideal condition, the early MKIs should have been retired by 2027. But since we're already short on fight numbers, IAF has decided to extend their life by another 10 years. So the early MKIs would start seeing retirement from 2037 onwards. Check this link: https://www.google.com/amp/s/m.trib...0-mki-fighter-jets-from-25-to-35-years-439010
And we're not looking to upgrade all MKIs. At max only 150 would be majorly upgraded, rest will see mild upgrades until they're retired.