Here's how long beancurd lasts:
Some time prior to July 12, I bought some Vitasoy Firm tofu at the Asian market. July 12 is the expire date stamped on the package.
I just opened it this afternoon, Aug. 12, and it seemed OK. Certainly didn't smell bad, and the water it was packed in, was still clear.
Since I rarely use enough bean curd at one time, I store it in brine (tap water + kosher salt). I change the water occasionally, and if I'm on top of it, the beancurd never goes bad.
I do the same thing everytime I have leftover tofu. I change the brine more frequently than "occasionally", more like every other day. It lasts long enough to be an incentive to use it, and just get it out of my fridge!
While you can keep it from spoiling, the flavor degrades dramatically, so what's the point? Tofu tastes best when eaten the same day it was made. It loses something overnight and each successive day you keep it.
Doesn't have to be stored in brine, either. If you keep tofu in fresh water, changing morning and night, it will stay good for a few days. Nothing wrong with slightly older, firmer tofu, for certain recipes, it's still fine.
From the Nasoya web site:
Nasoya Tofu has a shelf life of 70 days from the date of manufacture, which is represented by the Best Before Date stamped on every package.
Once the package is opened, any leftover Nasoya Tofu should be transferred to an airtight container. The Nasoya Tofu should be submerged under fresh water, whereby the water is changed daily or every other day, and stored covered & refrigerated. Following this procedure, the Nasoya Tofu will last 3-5 days.