What constitutes a WRITE cycle
The completion of a successful write to the memory cell or block of cells.

Flash Program Memory is erased/written in blocks of 32 words - or 64 bytes. So you have up to 100K writes to here before it gets into the failure range.

Data EEPROM can be written in single bytes - with up to 1M writes 'per cell' before it gets near end-of-life.

Just testing, i've pushed EEPROM memory beyond 5M writes, and it kept working just fine, but I wouldn't shoot anything like that out onto the market.....