Most packaged tofu is heat pasteurized, just like foods that are canned or fruits that are put up in jars for the summer. This ensures a longer shelf life, but it does destroy some of the delicate flavor of the tofu.
For a change of pace, try some of our un-pasteurized brands of tofu: "San Jose Tofu" or "Sacramento Tofu".
There are important differences in the way you store tofu at home, depending upon whether or not it is pasteurized:
The San Jose Tofu is received fresh every Wednesday around noon time. It should be taken home and eaten the same day for the best flavor. You can keep it up to 4 days as long as you change the water every day and keep it refrigerated. Texture is on the soft side.
The Sacramento Tofu (received Thursdays around noon), which has a slightly firmer texture than the San Jose tofu, is also un-pasteurized, with the added convenience of being packaged and sealed for easy transportation. Both of these tofu have more flavor than you will find in other brands. Of course, the trade off is that they are much more perishable and should be consumed quickly. Remember, even though the Sacramento tofu is pre-packaged like most other brands, you should open it as soon as you get home and change the water (and continue to change the water every day). Don't just throw it into the back of your refrigerator for using in a recipe next week, because it may be sour by then!
Most of the other brands of pasteurized tofu, like Azumaya & Hinoichi, can be stored for a much longer time in your home refrigerator. These should be kept sealed until you are ready to use them (think of it as a canned product). Observe the expiration dates, and try to use it a week or so before they actually expire (the shelf life is typically 4 to 6 weeks from the date of production). Once you open the tofu, taste it first to make sure it is not sour, especially if the date is close to expiration. Any left over tofu should be stored like regular un-pasteurized tofu: have it immersed in water and change the water every day. You can keep it another 3 days or so, depending upon how fresh it was when you opened it.