Skipping the usual rant about not buying from dropshippers......
I waited forty seven days for a bicycle chain before ordering from another seller.
Personally I allow 20 days from payment for delivery from North America and 30 from Asia.
Then a polite note asking for date of shipping, service used and tracking number.
If the response isn't satisfactory-- and most satisfactory at that point would be a full refund-- then I got directly to the Item Not Received dispute.
I don't believe there is any incentive for a seller to be honest if this is the procedure for cases like this.
You can start a Dispute for up to 30 days after the suggested last delivery date on eBay.
Paypal allows you 180 days from payment.
You can only leave feedback for 60 days from purchase.
A Dispute is much harder on a seller than you might suppose. In addition to forced refunds, a parcel delayed in the mail means he is out the value of the doohickey and of shipping as well.
Then there are Defects for being out of stock and for being recalcitrant about refunding. (Sometimes the refund to the buyer comes from eBay/Paypal which then go after the seller for their money.)
The Resolution Centre is at the bottom of this page.
The PP Resolution Centre is at the top of your account page, hidden under Tools.