We were at WDW last year for the last week of May, first week of June. We tried to buy tickets for the first e-night of June, and it had sold out. A couple years ago, on a different trip that was later in the summer, we got tickets for an e-night that we were later told by a cm had sold out. They do sometimes sell out, so getting your tickets asap is a great idea.
VelvetGloves