The information Allan Jones requested would certainly be helpful. Without it, all we can do is guess.
Are you referring to iCloud on Windows (from profile)? If you're looking to download the photos from iCloud to your computer, follow the instructions below (Download iCloud photos and videos - Apple Support):
1. On iCloud.com, click Photos and select a photo or video. Hold the command key on your Mac or control key on your PC to select multiple photos or videos.
2. Click and hold the download button
in the upper corner of the window. If you want to download your photo or video as it was originally captured or imported, choose Unmodified Original. For JPEG or H.264 format — including edits, and even if it was originally in HEIF or HEVC format — choose Most Compatible.
3. Click Download.
If your photos download as a ZIP archive, learn how to uncompress the folder on your Mac or your PC.
As for your second question, your photos won't be deleted after a time. Once your iCloud storage is full, you simply won't be able to store anything else in there until you clear some space (or upgrade your storage space).