From http://freeorion.org/forum/viewtopic.php?p=90438#p90438
An obvious remark: maximum efficiency comes from no using IS at all, since that way you are wasting no PPs in conversions.Vezzra wrote:First of all, it would be good if as many of you as possible would playtest the new mechanic in particular now, and give your feedback. I consider what went in as still very rough around the edges and in need of polishing before we can deem this ready for release. In particular the content provided needs a major overhaul, IMO. What we have is perfectly fine for playtesting, as it gives you easy access to the new feature in test games. But the Imperial Stockpile techs/tech tree and the fluff explanations can certainly be improved, and being able to use the stockpile definitely shouldn't be something available right from game start.
For particular purposes, like speeding up the production of something that you can not yet produce (requirements not met yet) so that you save for it in advance, or like getting some use for PPs that would have been wasted otherwise (supply lines cut off and nothing useful to do with the PPs of the secondary resource groups, appart from stockpiling them to use in the main group).
The former can be pretty stupid and better achieved by a proper scheduling of your research, so that you meet the constraints sooner (otherwise we are talking about either getting 2 or 5 PPs per turn, ridiculous, or having researched several IS efficiency techs instead of the requirements for your actual production objective.
The latter can be a seldom situation in which you were forced to expand far away via colony ships because there was nothing better than poor closer, and then I wonder why not giving more priority to growth techs. And it could also be, more often, the result of an enemy invasion of imperial space. In such case, I would prefer to produce military ships in each of my resource groups and figure out how to make the forces of each group to strike at the same time and place rahter than stockpiling say 60% of the PPs of the secondary groups for the primary one and waste the other 40%. In case I have 80% efficiency or better and I can spend stockpiled PPs at rates close to 50 or 100 per turn, then I can consider it a viable strategy.
Summing up, I find current stockpiling is a loss of time for any empire that is not struggling to survive an onslaught, and for such struggling empires is more like an entertainment for them to evade the idea they are getting wipped out no matter what they do (yet I prefer to improve weapons instead even if I'm going to die so that it not cheap for my enemies).
I don't disagree with this. Currently, the availability of IS from start gives no real advantage nor opens new viable strategies to any species. 2 PPs per turn that needed 10 wasted PPs per turn? No, thank you.being able to use the stockpile definitely shouldn't be something available right from game start.
Unless the starting stockpiling capabilities are boosted, that won't change with the expected major overhaul and having starting stockpiling will still imply nothing.
Maybe later IS techs could have way stronger capabilities and make the use of IS a viable strategy for scattered empires (probably stealth species).
Still thinking about all this, I may change my opinions without previous warning.