It varies a lot for me!
I definitely don’t post everything I come across. I respect that approach, but I like to get somewhere if I’m going for a walk - if I decided to post absolutely everything I would only be able to travel a few metres. :D
When I learn to recognise a particular new species (like a common plant), I often go through a few weeks of observing every single one I see. Because I’m excited that I can now identify it myself, and it gives me a sense of where it occurs and how common it is.
Often when I go out, I start with a rough idea of what to focus on - sometimes birds, sometimes moss, sometimes ferns, etc. I’m better at spotting things if I’ve got my vision ‘tuned’ to a certain category, and I like the fact that going to the same place can be different each time if I go with a different target in mind.
And there are some particular taxa that I absolutely always observe every time I see them, for various reasons. I love jays (guess why :P) but also have a history of never getting a really good photo, so even though they’re not very unusual I always try to record them. I observe every liverwort I see, because they’re so common and ubiquitous but also so rarely observed! I always record sundews, because their habitat is so specific that I’m always excited to find them.
So, it’s complicated. :P I am generally less likely to observe very common species like feral pigeons or grey squirrels in urban places. I feel like other local observers probably have those things covered, and I don’t think adding my observation to the pool will make much difference. Not that I don’t love those species too of course! :D