I've always used Win32 Disk Imager but assuming Balena Etcher is quite similar and creates a single partition that is only the size of the original 32GB SD card then you can use the raspi-config tool to expand the filesystem out to the full size of the new SD card.

Personally, I've kept my boot SD card on the smaller side at 16GB. I use a USB3 500GB SSD for the mass storage. I use symbolic links from the astroberry home directory to the SSD for large sets of files like the plate solving files and my actual imaging. This lets me make and save backup images of the SD card to my PC. It particularly comes in handy when Astroberry/KStars/Ekos is updated and you go to do a night of imaging and find out the update broke something. If you have a backup either in an image file or on a spare SD card you can quickly roll back without losing a night trying to figure out what broke.

You can do this with your 128GB SD card too. Backup/Restore is just slower and the cards are a little more expensive.

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