Customer Service at IRC, SP and P&C have told me the same thing, their current shipments of Penzance are at nearly the same level they were a year or two ago. The problem is that, because of the recent shortage, as soon as it's posted to their website they're flooded with orders and it usually sells out in a few hours. As soon as customers are satisfied that supplies will continue to arrive things should slack off a lot.
I expect the same thing to happen when the first shipments of Dunhill and Samuel Gawith arrive, they'll be gone in hours.