once a skill is activated it's there for good,  you can swap some of them over like the off/def boosts, if you want to boost your off you can click that one and it will boost off, if you want to switch that boost to def then you can,  there is also an option to use dracs to have BOTH of them on at the same time (hint  - only purchase those when there is an offer on and they get progressively more expensive) 

there is no cool down time when you switch them over  

extra points are carried over and go towards the next level 

Thank you for this information morteeee.

When you say that they get progressively more expensive, do you mean by the tier / level of the skill?  Or do you mean that each one you purchase will increase the cost of future purchases? 

by rank/tier 

Thanks guys... just one follow up question: The bonus that is labeled increase acropolis %x increase on carrying capacity. I know that I should already be aware of this but what does that actually do?

XP

increases the amount of resources your acropolis protects if you are successfully raided

Thanks for the replys!

XP