Never store a tent if it is wet. This will cause the fabric to delaminate and coatings to peel. Always dry out your tent before you pack it up for storage. Damp tents also mildew, which destroys the nylon and smells bad. If possible, let your tent dry in the morning before packing it up. If all else fails, pitch it when you return home. Sweep out all the dirt and leaves, sponge off dirt with a damp cloth, and hang it up to dry.
The sun too will eventually cause a tent to deteriorate. If possible, camp in the shade to avoid harmful UV rays. You might consider simply leaving your rain fly on during the day. They are easier to replace after a few seasons of abuse than the entire tent.
Tent floors can wear out, so use a ground tarp when possible. Thin polyethylene sheeting from a hardware store is a lightweight, inexpensive option to go under your tent.