Id say a good way is to cross country ski at elevation and when the snow melts then start hicking a lot at high elevation. Kill two birds with one stone scout and get into shape all summer long. Keep doing what you are doing but this summer get up above timberline alot and do what you will be doing on that sheep hunt hike like crazy with a big pack. Practice with more weight then normal so when you do go it will be easy. Good luck and happy hunting