Because I've prepared properly, the first take is often the one I end up editing and sending to my client. The second is simply there as a safety net, in case I need to replace any mistakes while editing. It's much better to capture such drop‑ins during the same session as the main performance, as you can be sure that the mic will be in the same place and your voice will have a similar character in both takes.
As editor, you need to turn the raw recording into the final version of the file you'll be sending to your client. Editing during a recording session can be problematic, and particularly so if you're recording in a domestic environment. How can you expect to hear the drone of the dishwasher ruining your recording if the dishwasher is still running as you edit? I'll look in more detail at setting up a voiceover recording studio next time, but for now, if recording in a separate room or isolated booth isn't an option, at least try to edit the file the following morning (or maybe at night) when there's less noise around — because hearing your recording with a fresh ear and in a quieter environment will help you to make better editing decisions, and will reveal noises that slipped your attention earlier.