It's not really Dish Pass; it is ANY timer that remains in memory to find NEW or ALL, as well. Since all instances of a program--new or repeats--are part of the total number of event memory, some TV shows, even limited to a single channel, can eat up your 576 total timer events. For example the following:
MTV can air The Real World as often as 20 or even 40 or MORE times (especially during the replays leading up to the final episode) in ONE WEEK. Now, add to that History airing Modern Marvels several times a week (they used to air it about 40 times in one week). Now add few kiddie shows that in total will count as airing over 100 airings per week (I'm saying a good 5 kiddie shows together could add up to 100). Now add the numerous other timers with more modest airings like 15, 10, 22. Now you can see that your 576 event memory is eaten up in short order.
Of course, as time passes and the events pass, memory is freed up, but can be eaten up again by new airings loaded into the memory.
Go to the menu and get to your Daily Schedule. Most likely Skipped Events are not shown and the # of events at the bottom right is NOT true number of events. To see the true number of event in memory select the SHOW SKIP button and look at the bottom right, and your should now see a humongous number.
Some of the most common work arounds for this limitation is to delete any unnecessary or out-dated timers of stuff you don't watch any longer or have seen all the episodes--as in there will never be any new episodes as the show is an oldie like on TVLAND or has been cancelled. See if you can use the Mon-Fri or Weekly timers because they do not load every instance of the airing in the memory. Keep your Daily Schedule clean and delete any repeat airings that should not be recorded by manually skipping that instance. I have found Big Time Rush on Nick is hogging up my events memory big time with tons of repeat airings, but Nick does slip in a new episode on occasion--sometimes one every 3-4 weeks--, so the timer can't be deleted or the DVR will miss the new episodes that are slipped in irregularly. Use Dish Pass carefully as a timer for The Golden Girls using Dish Pass will load into memory the 4 (or more) channels that currently air that show and several episodes back-to-back to boot. Those old gals are gonna eat up your events memory fast.
Personally, I think Dish should still add more memory to the events maximum number as I, too, have a lot of timers and I keep them because they have to catch the new episodes when they air months from now.
Good luck.