For the ICE exhibit, look for about two hours minimum. It's several degrees below freezing in there and the cold with get to you eventually. After the ICE show, there is a large stall of Christmas goodies to browse and the admission ticket includes a free hot drink, which comes with a live show, plus its in a HUGE hotel which is worth a good look round. Four hours should cover it.
Thank you for bringing this to my attention...I'm gonna take the wife there in the winter months to remind us how much we don't miss the weather in the NE