Ok final self-discharge results in. Not quite the result I expected, will have to rerun the test on the Imedions to confirm, but I can't think of any reason at the moment why the result would be invalid.
Spreadsheet of all results:
https://docs.google.com/spreadsheet/ccc?key=0AnF1KhnoruHSdDI5X2JVQ0ZXQzJaNlpqcklEU3dIOWc
Couple of graphs of self discharge results, including comparison of cells when new vs when used:
https://docs.google.com/document/d/1YH7pmlaoCnsoNWxzX-Wd4oZGKHRytP-ftwdizSY4GFQ/edit
90 day self discharge results
Average capacity remaining:
Powerex: 1878mAh (1931/1874/1830/1876)
Eneloop: 1726mAh (1727/1729/1729/1718)
Imedion: 1424mAh (1388/1291/1521/1496)
Vapex: 1047mAh (1068/923/1159/1038)
Capacity remaining as a percentage:
Eneloop: 86.3%
Powerex: 77.4%
Imedion: 62.4%
Vapex: 45.9%
Remaining capacity relative to powerex:
Powerex: 100%
Eneloop: 92%
Imedion: 76%
Vapex: 56%
Variability (stddev):
Powerex: 41.4
Eneloop: 5.3 !!!
Vapex: 97.4
Imedion: 105.8
The imedion result was odd because their self discharge seemed to accelerate from the 31 day test - they did well in the 31 day test and came second after the eneloops. My real world experience with imedions is that they hold a lot more charge than that at 90 days, however none of those real world cells have anywhere near as many cycles as these "used" test cells do. Also note there are different mechanisms of self discharge, and they take place at different rates depending on the charge level/voltage of the cell. I will put the imedions aside for another 90 days for a repeat.
Capacity of the now used cells, vs when they were new
Imedion: 99.6%
Eneloop: 99.5%
Vapex: 97%
Powerex: 88.6%
The poorer showing by the powerex here is borne out by my real world experience.