Long winded question, hopefully you can follow it My main source of income comes once a month and covers my bills and cash envelopes. My “other” incomes (random small jobs) contribute to my sinking funds. Some months are greater than others. Would you save ahead for future sinking funds once you’ve saved enough to cover your 2020 SF because of the instability of your income that covers those, or would you save the money in a different way? I’m afraid to lock up money in investments because my SF incomes vary greatly.