Are you asking about iCloud Photos Library or your My Photo Stream or Shared albums? There are several cloud services related to Photos by Apple. Te 2six months" limit might apply to iCloud Photos and iCloud Drive.
- Apple is shutting down My Photo Stream now. This service has been introduced to sync photos between devices for iPhoto and Aperture users. Apple has kept this service available for several years after iPhoto and Aperture have been deprecated, but will now close it permanently. It should not effect any photos you have stored in iCloud Photos or Shared Albums.
- There will be no changes with respect to Shared albums.
- The photos in iCloud Photos or iCloud Drive will not be deleted, as lang as you are having an Apple device signed into iCloud. If you have no longer a device signed into iCloud, and are no longer paying for the iCloud storage you are using, Apple is free to remove the data you have stored in iCloud after several months. You should not expect Apple to keep the data from dead accounts eternally.
- Apple closed down Mobile Me in 2012. All photos stored in Mobile me web galleries and journals have been erased in 2012.
If you are worried about your photos and videos stored in iCloud Photos or on iCloud Drive, as they are so precious to you, be sure to make regular Backups to have local copies of these items, and also ensure, that at least one of your devices is always signed into iCloud and you are not exceeding your cloud storage - keep your iCloud account alive. To archive your cloud data see: Archive or make copies of the information you store in iCloud - Apple Support