The T100MD+ PLC uses EEPROM that can endure rewrite of 100,000 cycles. This is nearly impossible to exhaust for the program memory under normal circumtances.
If you make use of the PLC's EEPROM data memory in your program, then just make sure that you do not have a rung that write to the EEPROM continuously every scan of the ladder as that will wear out the eeprom.
The EEPROM is replaceable if it is "worn out".