Hektore

If you're not slowing down enough to require a shift, there's no need to depress the clutch pedal. It may or may not be less wear on your gearbox, it depends on on how smoothly you shift (I would say you have to be nearly perfect in your shift to be less or equal). It's definitely more wear on your clutch.

I was taught it's best to have your car in gear, with the clutch pedal out unless you're actively shifting. This is for control reasons. The only exceptions is idling, where you can leave the car in neutral with the clutch pedal out. I was taught that it's lazy, but if your aren't going to shift through your gears to slow down, it's better to shift your car into neutral and let the clutch pedal out and come to a stop then to just hold the clutch down the whole way.

My teacher was of course my Dad, but in his defense he can drive most anything with wheels (including very large trucks), and quite a few things without. Also a bit by my grandfather who drove a large dump-truck as a delivery man for a quarry for a while. They're both pretty familiar with the ins and outs of a manual gearbox.

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The advantage law is the best law in rugby, because it lets you ignore all the others for the good of the game.