I've still got a tin from about 20 years ago that I haven't finished yet! I always wipe my strings down individually after playing and that seems to work fine.

Lemon oil is quite good for cleaning gunge off fretboards and I used it often as a repairer (I think almond oil with a little added vitamin E oil to prevent oxidation is even better) but it should be applied sparingly and infrequently with a piece of cloth rubbing sideways (i.e. parallel to the frets), preferably when the strings are off.

Peace

moo