Is there an app, extension, or add-on that will disconnect laptop from Pandora.com after a set time?

I like to fall asleep to Pandora but I do not like to leave Pandora playing all night on my netbook.

I primarily use Google Chrome and Firefox for Linux.

To disconnect now from Pandora, I just let the battery run down. Netbook shuts down in 2.5 hours. Is this my only option?