| Phanerozoic, currently | 22 |
| Phanerozoic or Archean, e.g. | 28 |
| Periods upon periods | 20 |
| Period from B.C. to TV | 22 |
| Oodles of time | 14 |
| One million millennia | 21 |
| One million chiliads | 20 |
| One hundred million decades | 27 |
| One billion years, in geologic time | 35 |
| One billion years to Hubble | 28 |
| No short time | 13 |
| Nearly infinite perioD | 22 |
| Nearly an eternity | 18 |
| Myriad coon's ages | 22 |
| More than two eras | 18 |
| Millions of moons | 17 |
| Millennium upon millennium | 26 |
| Many periods are in it | 22 |
| Many milleniums | 15 |
| Many many years | 15 |
| Many generations | 16 |
| Many chiliads | 13 |
| Many a doctor's office wait, seemingly | 42 |
| Major time span | 15 |
| Lunch ending | 12 |
| Lunch add-on? | 13 |
| Lot of time | 11 |
| Loooong wait | 12 |
| Longish span of time | 20 |
| Longest time division | 21 |
| Long, long time period | 22 |
| Long, indefinite period | 23 |
| Long time, even in the singular | 31 |
| Long time- | 10 |
| Long time division | 18 |
| Long stretch of history | 23 |
| Long spell | 10 |
| Long interval | 13 |
| Long historical episode | 23 |
| Long geological time | 20 |
| Lo-o-ong period | 15 |
| Lengthy time span | 17 |
| Lengthy stretch | 15 |
| Length of a boring class, so it seems | 37 |
| Largest geological division | 27 |
| Largest division of geologic time | 33 |
| Large timeline segment | 22 |
| L-o-n-g stretch of time | 23 |
| Kalpa, to a Hindu | 17 |
| James Bond film production company | 34 |
| Its make-up is many years | 25 |
| It's over thirty quadrillion seconds long | 45 |
| It's made up of many periods | 32 |
| It's going to be quite a while | 34 |
| It's a real stretch | 23 |
| It's a big stretch | 22 |
| It seemingly never ends | 23 |
| It might be divided into eras | 29 |
| It lasts between four and five galactic years | 45 |
| It lasts and lasts | 18 |
| It keeps going and going ... | 28 |
| It is a long, long, long time | 29 |
| It can be subdivided into periods | 33 |
| Interminably long time | 22 |
| Inordinately long time | 22 |
| Infinite ages | 13 |
| Indefinitely long time | 22 |
| Inconceivable stretch | 21 |
| Incomprehensible time span | 26 |
| Incalculably long time | 22 |
| Imprecise time unit | 19 |
| Impatient person's wait, seemingly | 38 |
| Immense time span | 17 |
| Immeasurably long period of time | 32 |
| Huge time span | 14 |
| Huge stretch | 12 |
| Half a million bimillennia | 26 |
| Hadean or Archean, e.g. | 23 |
| Group of eras | 13 |
| Great time expanse | 18 |
| Great geological time span | 26 |
| Geologist's unit | 20 |
| Geologist's time period | 27 |
| Geologist's measure | 23 |
| Geologic-time measurement | 25 |
| Geologic division of time | 25 |
| From B.C. to TV | 15 |
| Forever, more or less | 21 |
| Forever, facetiously | 20 |
| Forever and a day, facetiously | 30 |
| Extremely long stretch | 22 |
| Enormous span | 13 |
| Division of about one billion years | 35 |
| Cosmological unit of time | 25 |
| Cosmic cycle | 12 |
| Considerable stretch | 20 |
| Chiliad after chiliad | 21 |
| Century upon century | 20 |
| Billion years, easily | 21 |
| Big, big stretch of time | 24 |