I've only experienced this centre and the Aquarium in London, I have to agree that I love the fact that GYSC seems to have stood the test of time, and not become another 'Standard' Merlin attraction.
Like others have expressed, I often question why Merlin haven't invested more in the Yarmouth area, or indeed around the rest of Norfolk. The county is steeped in rich history, and various (and sometimes dodgy) myths, not to mention we've got our fair share of celebrities too.
I love our county, but we seem to be very stuck in our ways. It's time for fresh, immersive, experiences. I think Merlin could bring those experiences, and bring a massive financial boost to those attractions that are genuinely worth visiting, but are struggling. Traditional is great, everyone loves a bit of nostalgia, but there is nothing (other than maybe tight budgets.) that really gets families excited about Norfolk like a trip to London, or any Merlin attraction does. You know with Merlin you'll get something old, something borrowed, and something new. (And occasionally terrible IP choices, and even worse sponsorship choices, but we can overlook that!) Merlin have a real knack for taking something that has been done before, and turning into to something that feels fresh. Norfolk needs that.
As for only being open in peak season, I think much like most of Merlin's attractions, if people like something enough, they'll travel for it, I really don't think there would be an issue in trading all year round.
but that's just my opinion...