battery drain while on vpn

I noticed that if I have VPN on and not do anything on the iPad ( even sleep mode ), the battery drains down to low levels within 10 hours or so.

I have noticed the same on the 3GS as well.

Is this something well known or expected? or I should contact iPad tech support? Thanks for any info and guidance.

I am curious if it happens to others as well.

Bump, hoping to get some info from anyone else with the same problem.