Frankly I think 20 hours for 20 archers from a rank and flank is a bit excessive considering the basic color blocking could be done in batches saving a lot of time, but if someone really wants to put out an hour a mini for a troop rather than a centerpiece, siege engine, officer, etc. it's not entirely unreasonable nor am I going to tell them they need to speed up or slow down as it's their minis, and their hobby.
But at the same time, if you're painting 1 troop model an hour and you actually like the painting portion of the hobby, after a few years how could you not have more shit than what is playable in an individual list? But I guess if someone doesn't paint, they wouldn't be able to understand that, or grasp that a "dream army" doesn't need to be a specific bare minimum list and can include additional units for variety or even continuing to paint models for that specific army going forward simply because you like to paint no matter what your pace is on a per model basis. If you started the shit recently and it isn't a 10 model skirmish game, yeah it's going to be a concern if an update comes out the moment you're done with an initial list worth of units. Long term? It's a non-issue unless you're constantly jumping from army to army(so there goes the dream army or this is my individual guy that did some cool stuff idea) or game to game never to return(again, the silly arguments go right out the window due to no longer making any sense).