Template changes on upgrade (possibly daft) question

[Day_]

Feel kind of stupid asking this for how long I've been using IPB, anyhow.

For ease of this question say there is 20 templates in a theme, I have modified 5 of those, the other 15 are left as default.

When I upgrade, from 4.3.1 to 4.3.2, will the 5 I have modified remain untouched and the 15 default templates automatically updated as I haven't modified them, or do I need to go in and make the changes that are on the theme differences info on here? 

After every upgrade I've always just created a brand new theme, then made my changes, but not sure if I'm wasting time doing this.

[TAMAN]

All modified templates remains same after site update.

you can click on revert button on your modified templates after site update and then re add your customizations. you dont need to create another theme.

better yet, simply click on “Show default” button to see IF the template was edited by ips. if not then you dont need to do anything

[Day_]

And all unmodified are automatically updated then, awesome, thank you!