I never record in mp3 because then editing it, first off a lot of people don't bother saving off their file as a lossless format after, no it won't get back what NVDA threw away, but will make editing safer since editing mp3 is just a bad idea. Then if you don't do this, you're saving it and its a transcode of a transcode, at best, the same sample rate, bit depth etc, but if you change that then yeah. Each time through MP3 is chucking out more. I prefer to record in wav even though the files are large. But, my suggestion is that if you need to edit an mp3, import it into your editor of choice, save it off as a wav file, edit that, then only after its down and you want to compress it, then would I save it as mp3 again. Your editor is decompressing the audio when it imports it, still, if you edit and save directly off to mp3, sometimes you get weird artifacts in the file around your edits.
It is pure, free of judgement, and raises me to the utter height of glory.