How Long Shipping 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.
Dead drops and the window
A dead drop is posted to a shared location and collected by you. The window is set by the vendor and stated on the listing. Domestic drops run a few days. Cross border ones run longer, because the package moves through more hands and more checkpoints. The window on the listing is the number to plan around, and it is the one to trust.
What slows it down
A vendor with a high order volume ships slower than one with a light one. A route that crosses a border adds time. 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.