Maybe I'm uninitiated, but is leaving a Mac running under Windows actually that big a concern? Maybe Windows doesn't have all the thermal management capabilities of OS X, but generally the most critical thermal controls are done by the BIOS/EFI anyways. In any case, a CPU isn't going to overheat because of the various throttling modes (TM1, TM2) that activate to prevent this through hardware with no regard to the OS. The CPU will also automatically shut itself off and therefore the entire notebook off if throttling is ineffective. I'm fairly sure that both the chipset and the GPU also have similar features to turn themselves and the system off if they detect too high temperatures. Granted there's still the concern that prolonged high temperatures will shorten component life, but generally mobile components are designed for those conditions, and I would think one night or even if it happens occasionally is hardly a concern and within tolerances. It's really only if you do it continously for days on end that it really becomes a concern.