... firefox code base. What I can say is that the answer to that always depends. There is usually a way to guesstimate a reply based on the historical data of the project.

But what's *also* clear here IMHO is that the time to ask this question is *when a big change* comes.

It's always too late to ask this when several such big changes have been haphazardly flanged together.

But the question that is being asked instead is about benefit, not about TCO.