Globally it is inventory-backstocking that is coming onto the market, that's why there is so much available; I suspect though the stock will expire long before it is sold because digital continues to eat away at the market.
Velvia 100 is very, very contrasty and easily blows highlights and blocks shadows — far too easily and more readily than the stalwart RVP50. Velvia 100F is not the same as 100; the two also have dissimilar palettes and require tweaks of exposure. Reciprocity failure is the very least of your concerns with any Velvia emulsion. The trick is to expose all Velvias in the light they were designed for: diffuse or soft, and never bright point illumination which will show just how tempestuous the emulsions are. Sure, people use Velvias for weddings, that's their prerogative, but it's also a silly choice considering far better emulsions, and non-E6 at that.