Do "solid polymer" capacitors really have a longer lifespan than electrolytic?
Organic polymer capacitors, also known by names like OC-CON and trademarks like OSCON, give you a bit better performance than the best low-ripple aluminum electrolytic (ALE) capacitors at a higher cost, with a few caveats.
Ripple current for an OC-CON is generally higher than an ALE of equivalent size and rating. Good ALEs in the \$ 1000 \mu F\$, 16V range can have 100kHz ripple ratings around 1500mA - OC-CONs in the \$820 \mu F\$, 16V range can be as high at 5600mA.
OC-CONs are generally not as forgiving in terms of overvoltage as ALEs are. I've found that overvoltage will cause an OC-CON to fail short-circuit. ALEs seem to be able to take more overvoltage before failing.
OC-CONs also need to have charging current within a controlled range. Excessive charging current can degrade the leakage current performance or cause a short.
In terms of life, there are ALEs available with 8000h rated life, so there's no guarantee that every OC-CON will have longer rated life than any ALE. There are ranges for both. That being said, there likely aren't any 'general-purpose' OC-CONs with only 1000h rated life out there.
Sanyo has published this usage guide for their OSCON capacitors - the principles hold true for any OC-CON part in my experience (most manufacturers have similar documents).
For hobby use, you may be better-served by ALEs, since they're a bit more robust and cheaper. If you need the high ripple capability, however, there's nothing stopping you from using them - just be careful soldering them (see section 3 of the linked document). I haven't had any issues hand-soldering them, FWIW...
Yes, solid polymer capacitors will generally have a longer lifetime than wet electrolytic Aluminum capacitors (WEACs for now :-)).
The exceptions are special cases. The main lifetime degradation mechanism of WEACs is electrolytic dry out. When other factors are held constant, lifetimes are reasonably well described by the recently discussed expression
Life =~~ rated life x 2^((Trated-Twkg)/10)
ie lifetime doubles for every 10 degrees C below rated temperature.
Trated is usually 85C for consumer use and 105C for more severe (if not perhaps 'professional' use).
Rated life is usually 2000 hours, may be 1000 hours, and is usually a multiple of 1000 hours or perhaps 500 hours. You can buy 3000 hour or even 5000 hour caops BUT expect to pay. This coarse granularity reflects the inexact nature of the real life figure.
What this means is that WEACs tend to be easy to shorten the life of when things get hot or when internal heating occurs.
"Solid Organic polymer" caps do not share this main lifetime failure mechanism. Manufacturers rated lifetimes are typically 5 to 20 times longer, as gigabyte show.
If a 125 C 6000 hour WEACs was obtained it would notionally have an extended lifetime over a 2000 hour cap of a factor of 2^((125-105)/10)) x 6000/2000 = 12 times. This is > the 5 x improvement of some solid polymer caps BUT a very unusual and VERY high spec part. As polymer caps generally improve they will tend to be better than all but the very very very best WEACs. Expect to pay for it :-)
http://www.kemet.com/kemet/web/homepage/kechome.nsf/WebEn/KO%20Conductive%20Polymer)
http://www.kemet.com/kemet/web/homepage/kechome.nsf/WebEn/T520%20KO-CAP
http://www.kemet.com/kemet/web/homepage/kechome.nsf/vapubfiles/T520BTechUpdate/$file/T520BTechUpdate.pdf
http://www.kemet.com/kemet/web/homepage/kechome.nsf/file/T520%20Series/$file/KEM_T2015_T520.pdf
http://www.kemet.com/kemet/web/homepage/kechome.nsf/WebEn/T525%20KO-CAP
http://www.kemet.com/kemet/web/homepage/kechome.nsf/WebEn/T525faq
http://www.kemet.com/kemet/web/homepage/kechome.nsf/file/T525%20Series/$file/KEM_T2017_T525.pdf
Lifetime doubling per 10 degrees C decrease in operating temperature:
The doubling of operating lifetime per 10 degrees Celsius decrease in operating temperature is based on the Arrhenius equation which describes the change in reaction rates with temperature.
A web search on life of electrolytic capacitors provides many related links.
A few related references:
Capacitor life calulators - note the 2^x term for aluminum electrolytics where x is related to delta-temperature/1-.
Calculating the Lifespan of Electrolytic Capacitors with De-Rating
Aluminum Electrolytic Capacitors Life expectancy
Power Tip 50: Avoid these common aluminum electrolytic capacitor pitfalls - see 1st 'tip'
Wikipedia - capacitor lifetime and notes 93 94 95
Determining end-of-life, ESR, and lifetime calculations for electrolytic capacitors at higher temperatures