Erik:
For a detailed analysys of whether continued writes of 0xFF data to an already erased FLASH byte will lead to aging of the byte you really need to communicate to the manufacturer of the chip and see how the chip was designed. That point made let me comment...

- Some FLASH memories are designed with an intellegent write circuit that will prevent the application of the write voltage to the FLASH cells in the case that the cell content is same as the new data.

- It is partly the application of the write or erase voltage across a very thin insulation layer in the FLASH cell that leads to the degradation of cell. Another part of the phenomon is related to the tunneling process where by electrons are pushed through this insulation area in one direction or the other. If the continued excess writes that were going on went to a "dumb" style chip you could have degradation irrespective of whether the data was changing.

- Some FLASH chip algorithms for older memories used a "smart" algorithm that was driven by host software. This software if properly designed would inhibit the start of a write cycle if new data == erase data. So you should check if your chip type is one of those older types and also look into that part of the programming code.

Good Luck
Michael Karas

PS. I have heard several stories over time wherein some compannies products started to die after they were in the field for a period of years and find by tracing that the problem is caused by badly designed algorithms for FLASH or EEPROM. MJK