Something to note about caps is they have both a voltage and temperature rating. And while you might not see 85c temps in your case, if the cap is being used in a switch mode power supply or otherwise being exposed to high frequencies, it will have high internal temps. They get cooked from the inside. Having work in consumer electronic repair, I can say it is very common to use standard temp range caps in high frequency designs when extended range caps should be used. The result is bad/bulging or leaking caps. They may even look ok and test ok on a basic fluke. but need to be tested at the frequencies they are used at.
I also have seen countless boards where caps rated for 6v are used on a 5v line. That is not enough head room. And over time they will die. These factors will shorten the life a cap. Then there is the quality of the cap. A well made cap in a proper design for it's specs will last a very long time. But a cheap cap will dry out faster no matter how will the circuit is designed.
Oh, and when I say high frequency, I'm not talking about the Ghz you see in a modern computer, Even 100Khz can cook a cap.