Line spacer gaps in concrete driveway and sidewalks - ok to fill up gap?
From time to time, you will see crews going down an interstate or highway with air compressors. They will clean out all the joints and re-fill them.
This is not so important with sidewalks, because they should be tilted 1/4"/foot to allow water to run off, and the control and expansion/contraction joints are all parallel with the tilt, so water runs off, not in and under.
It is very common in this climate to see 4 corners coming together and smashing each other up a bit because of the expansion. This is with 1/2" expansion joints. Maintenance won't keep up and the joints will be left open over winter. They will repeatedly fill with water and freeze/thaw.
Next a crew will come in to replace these "4 corner" areas which have by now become pot holes. They will cut a diamond out, remove it, and fill in with new concrete. Hopefully they leave expansion joints, maybe even doubled up to 1". Then the fun starts over again and sooner or later they too need replaced and maybe the whole parking lot is done next.
I suppose the solution is to have the entire surface set up to drain better from the beginning. It would also help to have a grade below which would provide for drainage.
To answer your question, yes it is a good idea to fill the joints with some filler. And in a freeze/thaw climate it is imperative.