We've always kept some immediately-available cash in savings for those inevitable but unpredictable expenses that never come at a convenient time. The idea was at a minimum to keep enough to replace the car transmission, furnace, and roof all in the same month without having to tap credit.
One knows that such expenses are someday inevitable, but one cannot predict years away exactly when they will happen. But happen they will, eventually, just as sure as tomorrow's sunrise but hopefully not quite that soon. So when they did we could just tap into the savings set aside for that purpose and write a check to make the problem go away.
It never stops either. Just last week the 10-year-old microwave oven quit working and without having it diagnosed I can tell from the sound it's the magnetron, the expensive "heart" of the appliance. So we've ordered a new microwave, paying for it from that fund. No muss, no fuss, and life goes on.