Okay. I started the reinstall, of MSFS at 2030 (8:30pm 01/01/2021), a total of 107.69GB, and it finished at about 0040 (12:40am 02/01/2021). So it took 4 hours and 10 minutes to install it.
BUT... At  one point, during the install (at about 2330), while I was playing Cyberpunk 2077, and it froze on me. MSFS and CP 2077 were fighting each other for computer resources, so I had to exit the game (CP 2077). It took CP 2077 quite a while to shut down, and I was left with the game's main menu screen visible for about 5-10 minutes, unable to switch to anything else, including the desktop.

I still don't understand why it takes you 7 hours for you to get to 30GB, but I do know that MSFS takes far too long to reinstall. I have other games, that can be around 80+GB, and I can  usually download/install them in about 30-60 minutes, so MSFS at 108GB, shouldn't really take much more than an hour or two to install.