Geez, Carol that thing is gorgeous! I've honestly never potted up a brom, they grow so well on the ground under my oak trees. But what I'd do is tip it out of the pot and see what it's growing in right now. You've obviously been doing everything right for this plant. Try and give it exactly what it's had all this time. Mine grow in the leafy duff under the trees very happily.
Have you just been pulling out the spent rosettes of leaves and letting new pups fill in? Maybe take half the big ones out of there after they finish blooming and put them in the new pot, then that will give the ones left in the original pot more room to make new pups.
Unless you want to end up with 5 or 6 new plants from that one, that is. You could put each 'mama' plant in its own pot and let them all make pups separately. But I really like the grouping you've got there. That's the kind of clump mine make in the garden.
