Seven, so it takes multiple passes before it is done.
> Or was this more just a proof of concept thing?
Tough question :) No, it's for real it really has to sort through the 2000 kg, but if it needs to be beefed up or changed to get to the end then I'll do it. The next step 'up' would be a machine designed from scratch incorporating all the lessons learned with essentially unchanged software. There are still some limitations that could be addressed but then you'd lose the training set and you'd have to start all over from scratch. That might be worth it to get the last 1% error or so, so if this ever becomes 'real' then I'd have to do that. I highly doubt it will get to that though. time will tell.
> Plans to launch a Lego sorting service? ;-)
Not at present, though you're not the first person to think of that, parents with kids are suggesting I should make it mobile to visit people at their homes for $x / shot :) Still, that will only happen if I really have nothing better to do, which means likely never.
Don't sell yourself short. You built the thing, after all. Could be some fun road trips with, I'm sure, gracious hosts to entertain you during Lego sort. That could be a whole retirement life right there ! ;-)