Its pretty rare, for me, that I would ever do this so I hadnt considered it before. We did make a change in 0.85 so that when you opne the spellbook, the last spell you can is selected. For me the most frustrating part was having to look through the spellbook to find the spell again. Though that happened more frequently outside of the same stack casting if I was casting spells on multiple stacks, multiple cities, etc.