I would say the amount of overwriting for installs add negligible numbers of writes to the total life expectancy of the system.
The main wear and tear is on the mind...
Given APFS the best approach is to create container and install beta OSs into that. You can then use apps on the High Sierra partition. If there are large additional installs in Application Support that are not different, you can make symbolic links so they do not replicate. Same goes for DropBox, but not iCloud files. Mail folders, Photos Library, and iTunes databases will be different between OS versions.
This gives you a gradual and riskfree way to slowly migrate.
Containers on the same partition (disk) share free space.
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Set your boot drive to high Sierra and then do the update.
I just did it on mine and had no trouble.
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Looking at the Error display: With T2 Bridge drives are always encrypted. If they are not in FileVault mode, the first Admin password is stored somewhere, but might have gotten lost in your wipes. You will also likely find that you cannot get into the Startup Security Utility, because this token is lost.
Before doing anything else, boot and log into your admin account, if you can still do that. Then run this exactly in terminal:
sysadminctl interactive -secureTokenOn
YourUserName -password -
This will reestablish the token.
If I would have known that, I likely could have saved myself returning my system to Apple and having to wait fora replacement. This info is thanks to Mike Bombich - more here:
https://bombich.com/kb/ccc5/frequen...out-encrypting-backup-volume#startup_security