[mng2]

Agreed. Being a human pick and place for anything more than low tens of parts is incredibly unfun, and paying someone to manufacture one or two doesn't really make sense. I don't care if it takes a few days, I'd rather not be sitting for hours wearing down my fine motor skills and eyesight.

[thesmok]

If it takes more than an hour to place the components, your solder paste will likely flow all over the board and it will be pointless to reflow it.

[CamperBob2]

That's not a big concern for prototyping. It will reflow just fine. There might be a few solder balls rolling around afterward, maybe a bridge or two. Most of the time, this means your stencil apertures were too big, or that the cut-rate Chinese solder paste wasn't the bargain that it looked like on AliExpress.

Slump is a problem if you're trying to run a six-sigma process in a factory, of course, but that's not what's being discussed here.