Max duration of continuous video shoot for Canon 7D/5DM2

Hello,

During a discussion for a live event shoot, a fellow team member mentioned that a DSLR may have a maximum time duration for a continuous video shoot before the sensor overheats. Just wondering if that is so and if it is so, what is that max duration for 7D and 5DM2? A quick look at the specs of Canon 7D or 5DMk2 does not mention any such number.

Thanks,

Vipul