O-ring and oil applied to trs before each session. DA dryfire puts a lot of heat into the trs and can cause early failure.
Some years back I had a Witness Sport Long Slide (.45) that I dry-fired a lot, trying to smooth out the DA mode -- several hundred trigger pulls a night for weeks. I also polished the trigger bar and the inside of the slide. The only thing that ever broke was the bloomin' trigger bar, and I suspect that was just a fluke. Similar spring and a similar design.
I'm pretty sure that the trigger return spring gets compressed the same amount when firing SA as DA. The only difference is that in SA mode, the spring is partially cocked by slide movement. The only part of the trigger spring's compression that is likely to cause spring wear is the final part of the pull, when you're getting that spring closer to it's design (elastic) limit. And this is true whether you're dry-firing or live-firing. And with live fire, the heat form the round being fired will eventually work it's way into the trigger spring, too.
I think it's going to take a lot more heat than can be generated by dryfiring OR live firing a CZ to damage the trigger return spring. I doubt the oil is going to do to have much effect, either.