The number of write cycles varies depending on the device family and the junction temperature (Tj) during writing, but it is possible to write between 500 and 2,000 times.
For details such as retention periods, please refer to the datasheet for each device family.

[PolarFire]
Please refer to section "5.6.1. FPGA and μPROM Programming Cycle and Retention" in the "PolarFire FPGA Datasheet".
https://www.microchip.com/en-us/products/fpgas-and-plds/fpgas/polarfire-fpgas#Documentation

[IGLOO2]
"IGLOO 2 FPGA and SmartFusion 2 SoC FPGA Datasheet" TABLE 3-3: FPGA OPERATING LIMITS Please refer to the section titled "".
https://www.microchip.com/en-us/products/fpgas-and-plds/fpgas/igloo-2-fpgas#Documentation

[ProASIC3]
Please refer to the "TABLE 2-3: FLASH PROGRAMMING LIMITS—RETENTION, STORAGE AND OPERATING TEMPERATURE" section​ ​in "ProASIC 3 Flash Family FPGAs with Optional Soft ARM".
https://www.microchip.com/en-us/products/fpgas-and-plds/fpgas/proasic-3-fpgas