Hi, Sean,
This is AE team reply for large erasing time tolerance:
"
There is a footnote to describe the max. value: Maximum time based on expectations at cycling end-of-life. I think the erase time is affected by the physical characteristics of flash. These factors may affect the flash physical characteristics, such as production process deviation, the number of sectors/blocks erased, the length of flash operating time
"
Hope it can help you
BR
XiangJun Rong