[Alneyan]

Originally posted by oleg:
Do system-wide and planet-only condition improving abilities stack ? (I believe so)

Do several planet conditions improving buildings stack ? Probably not, but since Value improving do, why not conditions ?

I would believe system and planet effects stack, it is the case for other abilities, so why not for condition improvement?

As for your second question, here is yet another test.
Three level 5 CI on a Deadly planet, conditions 0.1 => The conditions are Harsh after 8 years, according to the calculations. (It takes around 25 years or so with a single level 5 CI, and 39 years with a level 3 CI) And it was only three CI, you could add a couple more to speed the process. (Seven years is all you need to transform a Deadly planet into a paradise with 10 level 5 CI. If you can afford it. )