Been there done that.Just on a short trip from my house to a friends I put my laptop to sleep,put it in my bag and drove to my friends,when I got there took it out and the fan was going nuts and it was scorching hot.Luckily it's ok.
i have always put my macs to sleep rather than shut down. my iMacG5 has never been shut down after use. its always goes to sleep and this has been since feb 2005. My old iBook I got in july 2004 has always been in sleep mode when not in use. only time i shut it down was in transportation.
i will say i do a restart every other week to clear up any RAM or whatever. only will shut down if i plan on not using the computer for a few days or when they are in transport.