Do you allow true expenses to rollover from one year to another? For example, if you didn’t spend your home maintenance in full in that year
Of course. The things I’m worried about happening don’t care about the date. It’s not as if my refrigerator goes “It’s January 1! I am renewed!”
Plus I have many savings goals which span multiple years, like buying a new car.
Now there are some true expenses you might be using to level out a purchase, like utilities, where you’ll want to assess them once a year, or a category you want to have a cap: e.g. perhaps for house things, you know that at $10,000 you’ve probably made a homeowners’ insurance claim. But in general, the default should be to continue to grow them.
Home maintenance isn't a good choice of category for this question. The recommendation for how much to save for home maintenance is an annual average, which includes short term inexpensive repeating expenses (air filters, fire alarm batteries, etc.) all the way up to expensive things like the new roof that happen every 20-30 years or replacing your kitchen appliances every 10-15 years. So the funding rule of thumb takes into account the short term inexpensive things and also the long-term large expenses. Which means you should never empty out the category, but rather allow it to accumulate.