I wouldn't necessarily do that for a wallhanging. If it ever needs washing, I would just hand wash it and lay it out flat to dry. It is the agitation in the washing machine and dryer that typically causes edges to fray; heat is usually the culprit in loosening fused fabrics.
It also depends on what fusible you used. Some fusibles aren't designed to sew through; they will gum up your needle if you try.