Hi JP, welcome to the forum! I forget what the average length of time is that fragrances are supposed to hold their structure, but I've heard it's anywhere from 2 to 3 years to 5 years, and some people say their frags last longer than that. So, don't worry about them lasting only a year. I think if that was the case, consumers would lose confidence in fragrance companies.
If you're really concerned that you'll never use up all your bottles, there's a swap and sale board on this site, and I know many people here treasure the Frederic Malle scents, as well as the others you mention, so you could decant (spray or pour) some of yours into smaller bottles and sell or trade them to other eager and willing Basenotes members!
As for storage, a cool, dark cupboard, closet or drawer should be fine. Some people do keep them in a fridge, which is advantageous if you live in the tropics. I suppose even some people in the U.S. do that, but I don't think it's necessary.
As to your Iris Poudre, I think it's all up to what you like to wear...many on this board don't care if a scent's labeled male or female...if it works for them, they wear it. If you're shy about wearing it to the office, just wear it at home and dance around! Or wear it to the movies etc.