I don't need my iPhone 6 to store full-res versions of all the photos and videos I've taken over the years, so I've enabled iCloud Photo Library and Optimize iPhone Storage. Unfortunately, enabling optimization means that even new photos get uploaded immediately, and it's not uncommon for me to review my photos at the end of a day only to have to wait a few seconds for each to be downloaded at a suitable resolution to view on my phone. This is very annoying.
I'd like a way to store full-res photos/videos on my phone for some time period I choose--a week, say. After that, the usual optimization would kick in: keep low-res versions on the phone, store full-res versions in the cloud, download full-res versions on demand. Is there a way to make this happen, either using stock iOS apps or perhaps a third-party app like Google Photos?
I have the use of cellular data to upload photos/videos enabled, because I want to get my images into the cloud as quickly as possible, in case my phone gets lost or stolen between times when I have wifi access. By the time I get to wifi access (e.g., at the end of the day after a hike), my photos have typically already been uploaded.