My best practice: whenever possible, avoid making relationships to edges and vertices and instead try to make relations to the SKETCHES that were used to create those edges and vertices. The extra effort only takes a couple of seconds (and maybe a little trickery using pierce and/or coincidence to get the relation to act according to your design needs), and it will save hours of time if there is a model change. I've recently saved myself man-days worth of time with this practice.
The reason is that model sketches are safe, while all of the edges and vertices in a model are constantly vulnerable to being absorbed by other features, can be wiped out by fillets and chamfers , their I.D.'s can be annihilated by split lines, and their location can change due to draft, etc. The only way that relations to edges and vertices is a wash when compared to selecting the foundation sketches is if you never, ever, ever expect to rollback and add features to a model.