I’ve programmed a thousand in one session (PIC32 QFN28 but in a similar ZIF contraption). It took about three hours.
That's only 10.8 seconds per chip. Depending on program length, flashing could take longer than that! Anyway you cut it, that is excellent output and probably a very long and tedious 3 hours! Did you make any special tools/trays to aide this process? Vacuum pickup tool essential, I presume? Did you have 2 set up so you could unload/load while the other was flashing? That's excellent overall time from taking bare chips in tube and getting flashed chips back into the tube, even if the flash took only 2 seconds!
sometimes it’s the only way
Maybe for you.
It was tedious, but then there are many jobs in one-man-band manufacturing and distribution which are like that, you just put the radio on and knuckle down. Almost always the thought of doing such repetitive and seemingly mundane tasks is worse than actually doing it. You usually fine tune your technique over time to become faster and faster: improving the process is part of the challenge and what keeps you sane.
I made a jig for the ZIF socket, and have a foot switch to start the combined programming/verify procedure. I place the parts one at a time in the ZIF with tweezers, but rather than closing the ZIF, I just apply a little pressure on the device down firmly but gently onto the ZIF contacts. This is far faster than having to open and close the ZIF door. I do a tube at a time, 65 or so at a time, and after each tube has been programmed I mark each chip with a silver marker pen, and put back in the tube.
Programming/verify is only 5s per chip, and another few seconds per chip for my manual tweezer, tube decanting and marker pen skills.
Most of the time I am able to plan and get Microchip to program them for me, but on this occasion they had no stock so I had to scrounge various compatible SKUs from a number of sources and program them myself.
Sourcing parts in volume was particularly bad around the time of the tsunami in 2012, it took about a year to settle down.