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Most soldering irons will last very well even if left switched on for long periods but the tip will eventually wear out, especially if you use sandpaper on them! Many soldering iron stands are fitted with a little sponge which you you keep damp to clean the tip. My preference however, is to use a silver foil scouring pad. They are very effective, last for ages and don’t seem to cause any damage.
When soldering, the idea is to heat both parts then apply the solder and allow it to flow. The trick is to do this as fast as possible to avoid overheating either the track or the component and damaging it. Keeping everything clean helps. The tip of the iron, the component leads and the copper track. If I’m using a home made board which hasn’t been tinned first, I clean the tracks with a little steel wool to make them shine first.
Also, it’s a good idea to keep an even, thin film of solder on the tip
