First MAC ever, battery charging queries

just bought my first mac ever 2 days ago, it's the new MacBook Air 13".
There are a couple of questions I would like to know about:

Firstly, when my MBA is plugged into a charger and the battery charges to 100%, does it keep on charging the Mac or does it switch to AC power and stop charging?

Secondly, if the answer to above is that it keeps on charging, then how often is it okay to charge my MBA?

Thirdly, as this is my primary computer I use it a lot! like A LOT! but my work is mostly browsing the internet and writing notes and as per the work I do I think the battery isn't giving the time it should. The battery lasts for 3 hours under the normal usage as mentioned above. Is it normal or should I get it checked?

GGJstudios said:

It stops charging when it's full.

There are many factors that impact your battery life. See the BATTERY LIFE FROM A CHARGE section of the following link for details, including tips on how to maximize your battery life.

Run on battery whenever you need to and plug it in whenever you can. You can plug or unplug any time you need to, regardless of the charged percentage, and you never need to completely drain your battery. Just make sure you don't run on AC power exclusively, as your battery needs to be used regularly to stay healthy. The link below should answer most, if not all, of your battery/charging questions. If you haven't already done so, I highly recommend you take the time to read it.

Apple Notebook Battery FAQ​

Click to expand...

Thanks for the quick reply. About the charging query, the guy at the store said that since unibody macs came out they don't stop charging when at 100% :s