An interesting thread.
I have to agree with Nick (and others) who say know what the flight manual recommends for each caution or warning light, and err on the side of safety. I've helped write some flight manuals, and I can tell you that a lot of debate, analysis, and testing goes into the emergency procedures. If you think you can second guess all this, while flying a helicopter, you're kidding yourself. Carry out the FLM procedure, and after you land start second guessing. Look at it, think about it, and then decide what to do.
Concerning "land as soon as...", this is where the pilot alone can make the decision. As one earlier post suggested, think about the worst result of the warning light (like a seized tranny, exploding engine, etc.), and only continue flight if landing right now looks worse. This is when having more than one engine can really extend your options.