I built my first rifle stock while in high school under the careful eye of an older gunsmith mentor. He mixed his own blend of oil using primarily linseed oil, a touch of varnish and china drier, as I recall, and he recommended one coat of oil a day for a week, one coat a week for a month, one coat a month for a year and one coat a year for life.
The exact formula was lost when my friend and mentor passed many years ago forcing me to search for a substitute. I didn't like one commercial "Linseed" oil because it obviously had way too much varnish in it (dried too quickly and didn't rub in worth a flip). I finally just diluted it down with pure boiled linseed oil until it was closer to the original oil.
Seems to have worked out OK; here's the stock 60 years later:
Beauty of a true oil finish is that small scratches are easily fixed by application of another coat of oil.
Regards,
hm