Apple Trade In (in the store), trading multiple devices, how long does it take

As far as I know, they allow multiple trade ins, but they will only be applied to your purchase of another device. If you are not buying anything, you will get a gift card to be used on purchases later. Do confirm that with Apple.

We cannot tell you how much Apple will offer for any device; it also depends on the condition aside from model and age. You will need to take it to a store to find out. Also cannot tell you how long it would take - depends on how busy they are.

Please understand that you are not asking Apple here. We are your fellow end users and can only quote from Apple document like this:

Apple Trade In - Apple (scroll down to see the FAQs)

or our personal experiences.

If you need to know more that what babowa has offered or what Apple wrote in the page I linked, please contact Apple. They will not see your question here. A support link is in the bottom left corner of this page.