It would be 9 years, if only one linear factor was at play.

I believe it’s multiple factors, though.

One is that every plane taken out had its share of “work”, which is now distributed across the remaining ones. Which means they get worn out a little faster. Similar to how they have to cannibalise parts from one civilian aircraft to repair another.

Then I’m going they cannot maintain the usual production speed because if the sanctions. Add to that an increased need to repair since the plains are more heavily used. And I’d guess that repairs are fine at the same facility that produces them, this also reducing production speed.

In other words, I think it’s about snowballing and at this rate it could be way less than nine years.