> >A good look at the Elna sheet referenced suggests that even very
> >modest fan cooling could double lifetimes.
>
> And what's the life of the fan? ;-)

Good question.
If you have a $10 head, buy a $10 helmet.

No name junk sleeve fan - low.
Quality ball bearing fan with certified MTBF from reputable manufacturer.
50,000 - 250,000 hours at 20 C say
20,000 - 50,000 at 70 C
Or more if you pay more.
One example of many:

              http://www.sepa-europe.com/pdfs/sheets/en/sfb25a05h-mfb25f12.pdf

Tiny. 50000 hr MTBF at 20C
http://www.switchesplus.com.au/products/sepa/ultraminature/sepa.mf10a.php

Rather cute
http://www.switchesplus.com.au/products/sepa/ultraminature/MF10A_doc_revised.pdf

ie you CAN get a fan that suits. And you can get junk.
BUT a fan's operation can be checked occasionally and as the job here
is lifetime extension of caps, fan failure is not a fatal event. If
fan can be replaced easily then doing this rather than replacing caps
may be attractive.
Overall design needs to look at implications of various failures.

Caps every 7 years MAY be entirely acceptable. Or not.


                        Russell
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