Local builds didn’t need to have certs updated weekly before at least. Doubt they do now.

If you have never had a paid developer account your provisioning profile is only good for a week. This period used to be 30 days but was downgraded to a week sometime in mid-2016, if my recollection is correct.

Apparently if you have had (or currently have) such an account, the period is longer.

You also can't use all the features of the platform, see the "Apple Developer" vs. ADP columns on https://help.apple.com/developer-account/#/dev21218dfd6.

Don’t local builds get the expiry date of the development certificate?

Yes, but if you do not have a paid account Apple will only give you a certificate that is good for 7 days.

Aah, I misread the comment I was responding to, sorry.