If you drop the slide on a 1911 without chambering a round, the slide speed is such that it can cause the sear/hammer engagement to jump or chip. Picking up a rounds from the mag slows the slide speed enough to prevent this. It is most prevalent in a firearm with a trigger job and a light let off. It shows up less in a Govt USGI as the trigger weight is usually between 6 and 8 pounds.
If you want a trigger job to last all you have to do is several things. Don't drop the slide without chambering a round, and don't buy cheap parts or mismatched one's. It's usually better to buy a hammer and sear as a set rather then play mix and match.
A good trigger job should, if done right and taken care of, last quite a while depending on the round count. I have a 60s NM 38special with an excellent trigger that has never been dinked with yet. It was used in competition in our area as I have photos and newsprint of the owner from that time. I got it when I bought the pistol from his widow.