Most historic sites are maintained either by the National Trust of Scotland or by Historic Scotland. Both offer memberships with free priority access and other discounts for a year or a lifetime - and have reciprocal arrangements with their English and Welsh equivalents. Depending on how much you get around and how long you are staying, they may well be worth buying... Membership also contributes to the sites' preservation and new acquisitions.
Historic Scotland
(http://www.historic-scotl...) - sites and prices, yearly membership starts at £34 adult, £65 family properties include Edinburgh and Stirling Castles. Historic Scotland also offers a 3-day Explorer Passthe National Trust of Scotland (http://www.nts.org.uk/) -sites and prices, yearly membership starts at £33 adult, £54 family properties include Craigievar and Crathes Castles, numerous wilderness areas