I have a different approach Frank! I very rarely switch blade sizes in the middle of a project. About the only time I do, is when there are long straight lines to cut, and that is when I'll switch to a nice heavy blade to make the straight lines easier to cut. When I reach that point, I usually just throw out the used smaller blade, because I'm approaching the end of the project anyway. Individual blades are cheap enough that I don't concern myself with getting every last possible cut with a blade before I throw it away.
If I switch blade sizes in the middle of a project for a different reason, it usually means I'm going to stick with the new size until I'm finished. In that case, if I haven't used the previous blade very much, I'll put it right back in with the new blades.