Most people don’t really budget for things that are large on a yearly or even monthly scale, but you can and probably should.
For example, I know that I use my headphones a lot and being without them would be really annoying. Budgeting based on buying them asap because I need them is a really painful way of managing that cost because I can’t do anything else at the same time and it is expensive. If instead I set aside a smaller amount while I still have working headphones it is much easier.
My formula for working out the cost is fairly simple. How much does it cost for an item to fill the need? How long do I expect that item to last in the worst case? How much would I therefore need to save per week for that cost to be saved before the current item needs replacement.
My headphones cost around $100. I expect to need replacement not sooner than about 16 months. So I should save $75 per year which works out to less than $2 per week. If I just save $2 per week I will hit my goal of $100 within the year and of something goes wrong earlier I can make the difference up the normal way. If I end up not needing a replacement by the time I hit my goal I can keep saving for a higher cost option or move that saving to another goal to boost that.
But things don’t just fail because of manufacturing defects. You can lose things, drop them, rip the cable out while moving a chair, … so many ways to break on day one that are not covered. But okay, I understand that you expect things to last at least a year, that is a reasonable minimum.
Yeah, I have dyspraxia which is basically medically diagnosed lack of coordination. I drop my phone at least a few times a day, I bang into walls and benches all the time, and I’ve fallen over so many times I don’t even get hurt any more. Along with the coordination I have lost or broken so many things in just this way, not to mention I am massive and most things are not built for giants. So yeah, a good number of items have been broken or outright destroyed shortly after purchase. No budget can handle that other than to just have more money on hand and to be as careful as possible. Screen protectors, rugged cases, and no open top drink vessels.