DLR has too many attractions and no real off season so they can't really avoid spreading out their closures throughout the year. It's rare to see a minor refurb between Memorial Day and Labor Day, but sometimes with the major ones it's unavoidable. When BTMRR had it's last major refurb it was planned for Jan-Oct and ended up being 14 months, so it was down for a whole summer. Last year the planned Peter Pan refurb was supposed to open for the start of the 60th but ran more than a month over. The Matterhorn also opened later, though it was still up for a media preview the day before the 60th and only went over by about 10 days, I think. It's best not to focus on what might be down because whatever they're saying now is likely to change up until a week before your trip.