We started buying the 10-Day No Expiration passes two years ago because we usually go to WDW for 3-4 day spans. So, we got three trips in with our first passes. We just upgraded to add the Waterparks & More package, which is great because if you do waterparks only days, you can double your Disney days (because the waterparks count as ten separate visits).
I had made a chart comparing the different types of tickets for us, but we purchased ours on the day before the price increase this summer, so the prices aren’t the same anymore.
If you travel 4 days or less at a time, then you’ll save money by purchasing the 10-Day NE tickets verses 4-day tickets. With 5 day trips, I believe you break even. 6 days or more, and you’re better off not purchasing No Expiration.
**We always buy the park hopper option, so it might be different with non park-hoppers.
We figure that even if we decide to go on a longer trip, those park days never expire. We can buy a package and save the NE tickets. We will always go back to Walt Disney World - sometime in our lives! It looks very expensive, but in the long run, it will save you a good chunk of money.