I suspect it would take a great many writes of a codeplug to bother an APX. I've got a 12 year old 7000 that has nearly 50 firmware upgrade writes and conservatively 500 codeplug writes on it over those years (mainly a guinea pig radio).
What I'd be more concerned with would be having the Instant Recall enabled. That feature has to put a much greater toll on the chip.
All of that being said, the APX uses modern flash memory (eMMC) vs what most think of as a traditional EEPROM chip. The exact type and capacity depends on the generation and radio model. The 7000 has 64 MB flash memory (coupled with 32 MB of SDRAM), while the 8000 has either 2 GB or 4 GB of flash memory (coupled with 128 MB of SDRAM). A bit of semantics, but nonetheless.
Most traditional EEPROM chips could endure around 1 million writes before degrading, whereas modern flash chips are a bit less resilient, with less robust implementations beginning to show degradation after just 10,000 or so writes.
Still, in the context of programming an APX, that's a hell of a lot of codeplug writes before you'd have to worry about it. But that Instant Recall feature...well....
