The fact that they leave sails fully rigged and tensioned (full downhaul and outhaul) is the best reason
NOT to buy used sails and masts from windsurf test and demo centers.
The masts almost always develop a "set" and remain somewhat bent in the direction that the downhaul put bend in them for several months.
All sails stretch a bit when first rigged from new, but sails that have been rigged for months with full tension tend to be stretched out well beyond normal.
So, they have lost some of their designed in shape.
As far as leaving your personal gear rigged, it's not a good idea. Might be OK if you let the outhaul and
downhaul off most of the way, but that streches the sail in a different direction.