I agree it sounds a bit excessive (though I go up to 50 tabs myself often enough), but how is you telling him off about how his way of tab-usage is inefficient

I agree it sounds a bit excessive (though I go up to 50 tabs myself often enough), but how is you telling him off about how his way of tab-usage is inefficient in itself in any way relevant to a discussion about browsers memory usage?? I hope you didn't really try to say "there's nothing wrong with browsers' memory usage, as long as you don't stress them too much" ? :) :)