Stock suspension life expectancy

MaysEffect

If you split the parts into individual categories, you get a better depiction on what goes bad first.

Springs - generally are a lifetime item that should not go bad unless they bind or go through horribly heat cycles. Lifetime for cars is generally considered 10 years and or 200k miles.

Dampers- this is a toss up. Under normal conditions they typical wear out somewhere between 60-120k miles. Bottoming out your damper or it getting clogged will destroy the life cycle.

Bushings - A huge proponent to suspension failure is bushing and bearing failures. Once these go, the above mentioned items will take on more abuse and wear faster. These can start to show signs of failure as early as 20k miles and can go bad with extreme abuse very fast (track days and long trips over poor roads). Bad bushings and bearings can cause higher torsional loads on the strut and mess up the damper even faster by binding and bending the main rod and seals.

Tire/wheel balance - often not considering a direct suspension importance, but an out of balance wheel or damaged tires will transmit more vibrations to the suspension and cause quicker wear on above items. First destroying the bushing/bearings which in turns messes up your alignment and then its a snowball effect from there. This is why its important to always check your tire pressure and routinely check that the wheel is in balance even if you don't rotate or change tires. Low tire pressures overnight will cause harsher flat spots that may go unnoticed to your arse, but your suspension will definitely feel it.