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I've read from conspiracy theorists that repeated formatting will reduce CF card life (they claim you should 'erase' regularly but not format), but I've never seen hard evidence to support this.
Here's a quick summary on the memory chips in CF cards:
CF cards have finite number of writes for each cell. That number if generally well above what most photographers will ever use. There are two types of Cf cards memory chips. 1)= Multi-layer (MLC) which has the shorter life between 15,000 and 50,000 writes per memory location. 2)= Single Layer (SLC) which has the larger number of writes before failure over 150,000 to maybe 300,000+ depending on the mfgr. SLC CF cards are more expensive. Most of the cards people use are MLC
Each time you write to a memory bit, it counts towards the total for that bit. Erasing is a write over action. The cards are organized such that you never actually write to just one bit, but rather write to a block of bytes. Thus the failure of one bit in a block will "kill" the entire block.
An "erase" on a card actually does more to shorten the card's life than a simple format. The format simply reorders the listing of available space on the card. It does NOT write to each memory block.. Where as an erase writes to the whole card, every block.
In practice, CF cards have internal controllers that attempt to "even out" the use over the card's blocks and that makes it difficult to ever truly securely erase a CF card.
And note that when you wrote "erase" in your post, I understood you to mean just that "erase" which is to write over the card's data and not to do a "delete".