Anyway, whether stochastic or not, I think I conclude on balance that the loss of a few Tranche 1 twin stick airframes doesn't make it onto my current list of most-worrying defence issues.
I do just wonder if the remaining pool of airframes, especially the 100 or so Tranche 2 and 3s, is quite big enough to rotate them through the front line out to 2040. Once upon a time there might have been a prospect of a small top up batch, but possibly not in the current climate.