How Long an Order Takes
The honest answer is that it depends, and the depends has a few parts. The vendor, the route, and the method. Digital goods are instant. Physical goods are not, and the gap between a week and a month is explained by a small number of things you can check before you order, not after.
Digital versus physical
A digital good arrives the moment the order is confirmed. There is no shipping, no waiting, no customs. A physical good is a dead drop, and a dead drop is posted to a shared location and collected by you. That physical step is where all the time goes, and it is the reason a physical order is measured in days, not minutes.
The factors that stretch it
A vendor with a high order volume ships slower than one with a light one. A route that crosses a border adds time, because the package moves through more hands and more checkpoints. A season with more parcels adds time. None of these are surprises, and all of them are visible in the vendor recent feedback, which is where the shipping complaints show up before they show up on your order.
Planning around it
If you need something by a date, order ahead of it by the stated window plus a margin. If the window is five days, order a week and a half out. The margin is not paranoia. It is the difference between a package that arrives and one that arrives after you stopped waiting.