In my experience, ( from France)
Shipping of items from China on ebay usually take from 2 weeks to 8 weeks
(But I just received an item that took 10 weeks to deliver).
Normally, after these 8 weeks, I will start to send an email to the seller telling him that I did not received the item.
Then I will let another week or two to show my good will for waiting, then I will ask him for sending another item.
This happened a few times and the seller always send the item, even if the delay for opening an ebay case was over,
and even the delay for giving a feedback ( 2 months, I think) was also over.
I never received twice these items, so the initial one was definitely lost.
Of course this was only for very cheap items. All electronic components from well rated sellers
( > 98%, most often > 99%).
For more expensive ones you need at least a tracking number.
On aliexpress, the procedure is more formal. Delivery are usually made with a tracking number, as the seller is only paid when you receive the item. So in some sense aliexpress is safer than ebay, but as you see, I had no problems with ebay.