Best practice on this would be to store the data in the excel sheets in a database. If you don't have that as an option, tableau does connect to cloud storage like onedrive, google sheets, etc. You could also store it there. Then Tableau would refresh from that location instead of your laptop.
Hope this helps!
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I don't use Tableau Online, so I don't have a ton of experience with it, but you should be able to use Bridge with Tableau Online to refresh your data sources automatically (without your computer being in the middle). See Use Tableau Bridge to Keep Tableau Online Data Fresh - Tableau .
You can use cloud storage for your files to get Tableau Online to be able to reach them directly, or you can use Tableau Bridge and upload those files to a shared location in a server, so Tableau Online would be able to reach that, without the need to have your laptop on 24 hours a day.