Backpacks/ Luggage

The hotel will store your bags in an office or closet during any of their reception opening hours, even if your room is not ready to occupy, or you have checked out. Many train stations also have either bag storage offices or luggage lockers for a fee; note the opening hours when you drop bags there so you can retrieve them in time.

Thankyou Wonderful. Yes it is a general Question as we will be staying at a mix of Hotels and VRBO places that do not have a front desk. When we check out at noon we will have several hours until the night train departs.

So I was looking for tips on lockers at Train stations etc. I may try tipping a bellmen at a upscale hotel to see if they could store the packs. Just looking for ideas. Thanks again for the response.

For train stations which have luggage storage (consigna) and the hours, navigate using this or click on the map - http://www.adif.es/AdifWeb/estacionesMapa.jsp?i=en_US - It will be a rare occasion.
Bus stations sometimes have storage. Sometimes there will be a private enterprise taking advantage of the train station not having the facility nearby, but I will be surprised anywhere will remain open until midnight. I have left luggage with a bar on a couple of occasions for €2 or €3.
And there are not many night trains these days so your concern over midnight is likely unnecessary.