Coincidentally I'm just now reading "How to make your electric guitar play great: the electric guitar owner's manual" by Dan Erlewine. He sepcifically mentions RAW linseed oil and said not to use the boiled variety.
Further, he says the stuff will keep a very long time - the tin he is using has been with him for over 30 years! Of course, he is not in Singapore - not sure if our climate will make any difference. Still he is a guitar tech which means he uses a lot more of it in his lifetime than any of us here. The trick (as he pointed out) is to use it sparingly on the fretboard and not to slop it on until it seeps into the fret crevices (with dire consequences).