| 100% | OED | 3 | Ref. work that took more than 70 years to complete |
| 69% | OED | 3 | Ref. work that took 70 years to complete |
| 68% | OED | 3 | British ref. work that took 70 years to complete |
| 68% | OED | 3 | Publication whose first ed. took more than 70 years to complete |
| 43% | ROME | 4 | City that took more than a day to be built |
| 43% | OED | 3 | It took 70 years to complete, in brief |
| 41% | THESES | 6 | Papers that take years to complete |
| 39% | OED | 3 | Ref. work whose first edition took decades to complete |
| 35% | PHD | 3 | Degree that could take up to eight years to complete: Abbr. |
| 34% | ROME | 4 | It took more than a day to build |
| 34% | TITANIC | 7 | British ship whose wreckage was found in 1985, more than 70 years after it sank in 1912 |
| 34% | OED | 3 | Ref. work that Tolkien contributed to from "waggle" to "wild" |
| 34% | OED | 3 | Ref. work that added "Dylanesque" to its lexicon in 2018 |
| 33% | NICETRY | 7 | "It's gonna take a lot more than that to fool me!" |
| 32% | OED | 3 | Ref. work with more than 300,000 entries |
| 32% | OXEN | 4 | Bovines that work more slowly than horses |
| 32% | ATL | 3 | 53-Down with more than 70 sts. that have a form of "Peachtree" in their names |
| 31% | PERENNIAL | 9 | Describes a plant that lives more than two years |
| 31% | LIFESWORK | 9 | It takes years and years to complete |
| 31% | GAMEOVER | 8 | Message that might prompt you to take out more quarters |
| 31% | HOG | 3 | Take more than due |
| 31% | HOGS | 4 | Takes more than share |
| 30% | MAMA | 4 | Parental term that is phonetically more difficult to say than "dada" |
| 30% | BITING | 6 | Taking more than a nibble |
| 30% | ODES | 4 | Works that take serious dedication? |
| 30% | REDPILL | 7 | Truth that might be hard to swallow, in more ways than one |
| 30% | CIA | 3 | Org. that you can't admit you work for to most people |
| 30% | PERENNIAL | 9 | Term for a plant that lives more than two years |
| 30% | KOI | 3 | Fish that can live more than 200 years |
| 30% | LOBSTER | 7 | Crustacean that can live more than 100 years |