There are insects that only live for one night, and never see sunlight. Other organisms have even shorter lifespans. If they could contemplate how long we human beings live, they would likely find it unbelievable. So it makes sense that we should find Brahma’s lifespan incredible. But considering how quickly any amount of material time passes—relative to eternity—we expect that even Brahma would consider his life too short.
There are insects that only live for one night, and never see sunlight. Other organisms have even shorter lifespans. If they could contemplate how long we human beings live, they would likely find it unbelievable. So it makes sense that we should find Brahma’s lifespan incredible. But considering how quickly any amount of material time passes—relative to eternity—we expect that even Brahma would consider his life too short.