In crypto mining there is _only_ short term because if you haven't made your money back in the first few months you are in the long tail and will never break even.
For any algorithm that hasn't gone ASIC, residual hardware value is paramount. A previous generation GPU will still be worth something on the 2nd hand market to somebody looking to build a gaming rig.
What do you envisage an FPGA to be worth on the 2nd hand market when it is no longer clearly profitable for mining? How many FPGAs have been through ebay in the past year vs. how many GPUs?
IMO realistic residual value potential of an FPGA needs a long, hard look in the cold light of day.
This is ABSOLUTELY wrong.
People who started mining five years ago got their return on investment after 36 months so your argument is demonstratively false.
There is no recent FPGA available on ebay because simply said only developpers buy them untill now and they need it and have no reason to sale them via ebay. They will sale them on specialized website or via forum of devs.