Tom,
I've had a set of TI-JFs on my Series 2 shortie for three years, and while I'm not sure they continue to improve with age time hasn't done much to take the shine off of them.
Most of the treble comes off with age, I've found, and the rest tends to be buried in the mix. As far as the playability goes, once you get used to them they're great...your touch has to be very gentle and precise to get a tone out of them, but over time my technique has improved a lot from this.
You'll need at least the medium-scale set to fit on a short-scale Alembic...I have long-scale strings on a short-scale bass and the silks stop short of the nut. If the medium-scale set fits, they should have firmer tension than my set, which plays pretty soft because the string diameters are narrow on mine, .085 on the E string I believe.
As far as the price goes, where did you get that quote? Mine came from the Vintage Bass Trading Company (vintagebass.com), and Steve's prices are a damned sight lower and come with great service to boot.