Long ages are a recent phenomenon to justify evolutionary philosophy. I used to believe the day-age and/or gap models were credible, until I realized they had a number of linguistic and logical problems, and that my view was not based on the Bible’s language or historical views, but simply to accommodate long age concepts. These models were constructed in the nineteenth century in an attempt to harmonize evolutionary dogma with the Biblical text. Long ages were touted as ‘proven’ by science, and therefore it seemed necessary to force the Bible’s language to conform to this supposed scientific fact even if this created linguistic, logical and historical inconsistencies.
See how this came about at Young and Old Earth Creation Beliefs and Origins.