[sershe]

A much simple explanation is that each order is assigned a priority f(elapsed time, is prime) prime orders starting much higher so the processing of your order gets delayed behind all the incoming prime orders until its priority catches up due to longer elapsed time

[bombcar]

They obviously have some metric that if you buy something, you’re likely to buy something again within two days so by holding the first shipment until you do the second purchase, they combine shipping and save costs.

[al_borland]

When ordering without Prime it says you have 24 hour (I think) to add other items without incurring additional shipping charges. I don't remember Prime doing this, and there is little benefit to the customer to care, because it's all "free" anyway.

I ordered something on Sunday, I had until Monday to add additional items. I was charged on Wednesday evening, it shipped Thursday (today), and should show up tomorrow.

I can buy the priority method. Sit it on until a lull in demand, or 3-4 days pass, whichever comes first. That's how it feels.

Even though thad had this order for 4 days so far, they are effectively giving me 1-2 day shipping once it finally ships.

[kjkjadksj]

Except they don’t combine shipping on separate orders afaik