I purchased my Navionics Cards 3-4 years ago and I assume there is a ton of new info to be downloaded. How often is it recommended to update the card and what's the best way to go about doing it? Thanks in advance.

That depends on what you want. The depths of the lake are as accurate as the survey performed. There are some changes, but not as much as one would think to our lakes. If you want the most recent hot spots or community edits, yes, upgrade. If you are just using it to find navigate or inland waters, general areas for fishing, and then using the graphs to find the structure/cover you want, it may be of limited use to upgrade. That is unlesss you go with the "freshest" data and get a year of downloads for the lakes you want. Those community edits can be downloaded separately, and may allow you to build maps using your sonar logs (real-time in some instances).

What card is it that you are running? If it is a platinum you can update it online with the 1 year of freshest data that David mentioned above. If it is an older Platinum card, and it will not let you update, you can call Navionics customer service, explain you have an older 2gb platinum card, and they will send you a new platinum for the same $99 with one year free updates as well.

As far as updating the areas you fish, you can check out the webapp on the Navionics website. It is the most updated mapping available (once you toggle the sonar chart button in the bottom left), and will allow you to view the ares you fish mostly to see if paying for the updates is right for you, before spending any money.
http://webapp.navionics.com/#boating@6&key=omvvDnjx%7DP

I checked my cards and viewed the website data and I think I'm good for now. Thanks for the info guys.

Ok maybe not good. I went back through my chart options to make sure everything was set correct and it want allow me to check the fish n' chip selection. My units are Lowrance Gen2. Any idea how to turn the fish n' chip option on?

They may be old enough that the FishnChip layer was not available yet, which is where you would want to do the update via the calling customer service so that they can get your platinum cards replaced with the 16GB cards.