And when we say 6 months in-game time.. we're talking roughly 1 month in RL 
how many in game months equal i real life month?
As Drah pointed out, 1 month of real time does certainly seem to be
roughly 6 months in PS time. One hour in-game lasts 10 minutes of real time. So, why did I say 1 RL month is 'roughly' 6 months in-game and not 'exactly'? Well, it appears to me at least that at least one (maybe all?) months in Yliakum have 32 days in them and I believe there are 10 months on the calendar as well, making the number of days in a year about 320.
But, you can roughly divide game months by 6 to have a good approximation of real months if you want to add the feeling of a certain amount of time passing for your character. If you want a pregnancy to last 1 year for your character, then there are a few ways of approximating the real-life time:
(calculations approximate for simplicity)
10 months IG /6 = 1 1/2 months RL
45 weeks IG /6 = 7 1/2 weeks RL
320 days IG /6 = 53 days
So, as far as I can tell 1 year IG = 1 1/2 months RL = 7 1/2 weeks RL = 53 days RL. I hope this gives you an approximation anyway.
Edit: I would also be interested in what the average lifespans of the various races are.
You're not the only one. I am quite interested in this myself. Check this thread out:
http://hydlaa.com/smf/index.php?topic=22968.0I think I brought up gestation periods in that thread as well. The two kinda go together as they are part of the natural lifecycle.
*Edit: Corrected mistake. An in-game hour is 10 minutes, not 6. I knew something didn't add up right.

Also, Miadon, I like your chart below better than mine.
