I want to use your post to point out that I think that everyone has the timeline of the Calm off. I always assumed that it last a few months, maybe a year or two, but no longer.
Keep in mind that Lulu's supposed to be, what? 22? 23? I know she seems older, but Yuna's only 17. The oldest I'd guess her would be 25. So, let's say that she was 25, and Braska's Calm started 10 years prior. If it lasted a year or two, that'd put her at 17 when she was first a guardian with the girl in the Cavern (can't remember her name) and maybe 20 or 21 with the guy who became a monk.
Of course, I could be totally off, too. Especially with the monk's pilgrimage. But the game seems to imply the girl's pilgrimage was several years before the game.