JD, are you currently making your own profiles, and if so what hardware/software are you using? I've used one Hahnemuhle paper that had a 5 year batch difference, and there was so little difference in the profiles that I put it down to measurement error or rounding errors in the software. Measured with an i1 pro, ECi2002 CMYK target, Printopen 4. That was all one batch of ink and simply on print run to another on the same day.
Yes some paper does "drift" a lot from batch to batch, but the really good stuff should be very consistant.
Now ink batch to ink batch may be another story altogether. Even Epson inks are only good for about a 3% difference. That's normally less than 3 DeltaE and so not normally visible.