Removing the battery is typically specifically warned against.  Desktop mode battery charge will basically cause the AC adapter to NOT keep your battery topped up all the time.  Instead, it will supply power to the system but allow the battery to naturally discharge down to a certain point (sometimes you can choose the percentage level) and only start charging it at that time.  And sometimes you can tell it to stop charging before 100% in order to increase battery longevity.  I use this myself because I too almost never take my laptop with me.  The potential downside of course is that if you need to take your laptop with you while the battery has self-discharged, you may not always have a full charge ready to go.

That said, batteries last a lot longer than 6 months.  Typically they'll go 2.5-3 years before having lost a meaningful chunk of their usable capacity.

Hi Mani Kandan,

Thanks for posting.
The life of batteries is determined by the number of charg-discharge cycles, so removing the battery completely will not change the way it's charged.  Some helpful information from the link you provided is:  

3. How to extend your battery life?

Batteries need regular usage to mantain healthy charge levels. To keep your battery healthy follow these recommendations:

• Do not leave your system plugged for extend periods of time
• Drain your system battery completely and then charge it while it is of at least once a month

Here is some more information from the Dell knowledge base: pilot.search.dell.com/laptop batteries