I wouldn't know because I don't have their numbers, and unlike you, I don't trust my offhand estimates.

However I will trust the Ukrainians to know, and it seems safe to reason that the more and better arms they have -- the farther off the potential triggering of such a limit will be.

The key consideration to keep in mind here is that for Ukraine, the fight is existential -- while for Russia (as a country, apart from its leadership) it is very much optional. So the limits for what is bearable in terms of any category of loss must be weighted very differently (apart from the what the numbers might say; and assumes we even have reliable numbers, which of course we don't).

So the flip side of your question might be:

"For how many years does Russia want to keep spending 10 percent of its GDP on this little expansionist fantasy project gone horrible wrong? And how does this math change once Putin is gone, or his lights start to dim?"