We go every month, sometimes every week and my girls (3 and 4 y.o.) can't get enough. We've brought many out of town guests in (they allow 5 in for free per visit w/ your membership) and it's always been a hit, especially when there are little ones. The membership is well worth the price since you get free passes for other museums in the nw, imax passes, and discounts in their gift shop.
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