expiry date on downloading photos

You can use iTunes to sync photos from a folder on your PC to your iPhone, see this link: Keep your photos safely stored and up to date on all your devices - Apple Support

(scroll down to the paragraph "Sync your photos manually with iTunes" )

When you sync with iTunes the new sync will replace the older synced photos on your iPhone.

If your photos are in folders on your PC, sync like this:

1. Organize your images into folders and subfolders.
2. Plug in your iPad or iPhone to your Mac or PC.
3. Open iTunes, if it doesn't open automatically.
4. Click on the iOS device icon in the top bar, then click the Photos tab.
5. Check the "Sync Photos" box.
6. Select "Choose folder" from the drop-down menu.
7. Browse to your desired folder.
8. Choose to sync "All folders" or "Selected folders", and whether to include video.
9. Click Sync in the bottom right corner.

On the screen is a message - "Iphone 6 Plus can access photos in icloud. Photos can be downloaded to your device via WiFi or Mobile network."

This message will appear, if you enabled iCloud Photo Library on your iPhone. Then syncing with iTunes will be enabled. In that case you can either use iCloud Photo Library to transfer your photos, or disable it on your iPhone, if you do not want to use it.