Thank you all for your valuable comments.  I think I will continue submitting the maximum size to all sites as I have done up to now.  As many of you said the value of larger files is the ability to crop or to rescue files with problems such as those shot at high ISO with too much noise.

yes...too lazy to minimize them and too time consuming to do so too.

Not at all. I use xnview (freeware) to downsize hole folder with 2-3 mouse clicks. You can do the same with photoshop's scripts.