Here’s my take.
Would you rather have dozens of photos of the same critter, or just one or two higher quality images?
I think it is best to have a balance of both. With things like fungi, having more pictures lets you see more features of the organism so you can best identify it. Many people take one picture of the top and call it good. I need to be able to see the gills!
What about resolution? Just enough to ID the critter? Or do you want to be able to blow it up to see the critter’s parasites?
A blurry, low res picture is only of little help - but post it anyway! As far as I know, images over a certain size can’t be uploaded, which is why if I am using DSLR photos I downsize them when I export for use on iNat. Again, though, more detail = more better! And if your pictures are not only informative but good looking, researchers may want to use them for publications!
We’ve been in this house a few years. Is there an age limit for older observations?
Post them!! Just make sure they are dated correctly.
Put very simply - any data you share could be helpful to someone. It doesn’t have to be good! Just put it out there!