If it’s the same individual on the same date at the same place, all the photos should be placed in a single observation. Here’s somebody’s copypasta that I’ve used to deal with this: "Hi, it looks like photos of this organism are uploaded as separate observations. On iNaturalist, multiple photos of one organism taken at the same time and in the same place should all be uploaded as one observation. If you have accidentally uploaded images as separate observations when they should really be combined into one, here is a tutorial which tells you how to combine them: https://forum.inaturalist.org/t/how-to-turn-multiple-observations-into-a-single-observation/9838 "
If they’re exact duplicates, I ID and go on. Sometimes make a comment that they’re duplicates and one should be removed, but that takes more time.
I think it’s really helpful to ID all the duplicates or all the different observations of one individual because after IDing one I can do the rest quickly and that reduces the time other IDers need to spend on them. Of course, sometimes that gets annoying.
If they’re photos of the same individual organism observed on different days, it is nice to add a link between the observations. I usually do that in a comment that gives the observation # or URL of all those in the series, but I think there’s a more efficient way that others know about.