The "lifetime rating" such as 5,000 or 10,000 hours is a minimum for operation time at the rated specs (voltage, temperature, ripple, etc.) without the capacitance value changing more than a specified amount (such as 20%.) Doesn't mean it will start leaking at that point. And if you significantly derate the cap by selecting one with a higher voltage rating, operating it a lower than rated temp, etc, lifetime can increase by a lot. However, most manufacturers recommend a 15 year lifetime (calendar, not operating time) due to deterioration of the sealants. So EL caps do degrade over time, but you can slow it down, just check them after 15 years...

Mike