Query on camera storage & Extreme SD card

Hi Friends, I just bought a Nikon D90 with kit lens 18-105 VR.

Have a couple of queries:
1. When keeping the dslr camera in the camera bag, is it better to keep the camera with lens attached OR we need to detach the lens & keep it separately?

2. Is the Extreme SD card (like Sandisk Extreme) essential for dSLR cams?
I have a normal 4GB SD card.

Q. When keeping the dslr camera in the camera bag, is it better to keep the camera with lens attached OR we need to detach the lens & keep it separately?

A. Keep the lens on the camera at all times to avoid letting dust and humidity into the camera. When changing lenses choose a spot out of the wind for the same reason

Q. Is the Extreme SD card (like Sandisk Extreme) essential for dSLR cams?
I have a normal 4GB SD card

A. You would need a Class 6 SDHC card if you were shooting a long video sequence or a long burst of RAW. For normal shooting you can use a Class 4 SDHC

Many Thanks Franglais for the info!

Charles gave some good reasons to keep your lens on the camera and I will give you one more very important one. By having a lens on the camera and ready to shoot it may keep you from missing any shots that pop up. If you have to take the time to put things together it may take too long and cause you to miss the opportunity. I always keep lenses on my cameras, Jeff

Thanks Jeff for the confirmation!

Charles, I just noticed I have a Lexar Class 2 SDHC card (4 GB), is it good enough?

OR should I get a Class 4 SDHC card?

If you are shooting HD video, the better choice is at least 30Mb/sec transfer rate. Other cards will cut out from about 30 seconds because of slow transfer rate and the buffer filling up. The camera stops functioning and becomes a useless paperweight until the file is transfered, and takes such an agonizing while! For Nikon, the highest rated cards can only allow 5 minutes of continous shooting before it cuts out, if set on the highest quality mode. Low quality gets you 20 minutes.