Wise advice, Martin. As a rough rule of thumb, perhaps the piquets should be no further out than the limit of rifle fire (24″ in these rules)?
I am aware that in more modern conflicts, radio contact gives a recce force the opportunity to pass on intell. & to seek succour if things go awry.
Going by your view, a scouting force, too far out, might just disappear without trace: no use to the force commander & not a lot of fun for the scouts.