Edging has a number of benefits. One is that it helps you delay orgasm by becoming accustomed to the "Edge". Another is that it gets you to 100% erection, which is good for several girth exercises. There are theories of releases of chemicals when you edge, Supra did some research on cAMP and cGMP - good for girth exercises.
When I edge throughout my girth session I find it easier to keep my erections and get a better workout. Some have reported gains through concentrated edging sessions alone.