I tend to buy extra of whatever has broken. There's no telling what would go next. But I always have a supply of oils and car liquids, filters, etc. Have always done this, enough for a year.
Same goes for food, tend to buy in large lots and store it. Have some backup stuff for personal care and emergency supplies. But no one can have everything...
It's a very good practice to buy two when you need one, especially if the parts aren't super expensive, it makes sense.
I tend to double up where I can when things are on sale food wise on non perishables. It's always difficult to work out what we would need but it's always better to have a bit more than just enough. I just wish I could grow more of my own greens.