Under normal, aka moderate use, a woofer can last a very long time. Decades, even. A lot of things can affect their lifespan, though. A woofer living in a relatively persistent rain of spilled drinks will not live as long as one kept in a nice, cool, dry environment. Gravity can also influence its life. If the cone moves vertically, there is more force pulling the woofer down, and that can eventually lead to the coil becoming offset in the gap. If the cone moves horizontally, it's much less likely for sagging to occur, but rotating the driver 180 degrees once a year would prevent any misalignment from happening over time.
So what about extreme use? Woofer suspensions wear in a pattern similar to tire wear. The harder you drive them, the sooner they wear out. With intense usage, the suspension of a woofer (in a sub and also in a top) can soften and stretch over time. This happens very slowly with normal use, it's barely noticeable and barely measurable. (Comparison would have to be made with an identical new unit in the same environment with the same components and programming to detect the changes.)
With intense use, this deteriorating happens much faster. Most surrounds and spiders are made out of cloth, and that cloth is pressed into shape (the ripples) using heat, and held in place by chemical and adhesive additives that are embedded during the pressing process, or added afterwards, or both. (The parallel here would be starch in a shirt.) The fibers in the cloth and the bonds in the adhesives break down over time, and the harder and more often they are stressed, the faster they lose their original shape and resilience.
Eventually a woofer's resonance can fall below the range for which the cabinet is designed, and a slight loss of system sensitivity can be the result. The driver's average sensitivity doesn't change but it becomes mis-aligned with the cabinet's tuning. Usually the tell-tale symptom is that the driver(s) will start to bottom-out or "pop". Sometimes, before that starts to happen, slightly more distortion will be noticed, particularly from the drivers' surrounds, which become softened and may buckle under higher pressures where a new woofer's surround would not. Essentially the suspension components of the woofer are wearable parts, and as with tires and shock absorbers, they need to be replaced when they are worn out. There are 2 options to restore the performance to as-new. One is to re-cone the woofers. This is less certain because you're depending upon the skill of the person doing the labor, and their assurance that they have provided the original replacement parts, but it _sometimes_ is cheaper. The more certain way is to replace the woofer with a new one.
Since the amplifiers have no moving parts, they are much more consistent over time, and when one is failing, it's usually very obvious. Replacing a woofer gives an old speaker a new lease on life, so rather than replacing the whole loudspeaker, maybe a new woofer is all you need.