The first weeks.
IMMEDIATELY
Confirm the site loads from another device and network Confirm HTTPS works with no warnings Submit your sitemap in Search Console Confirm analytics is recording Test the contact form from an external address Check search engine indexing is enabled
FIRST WEEK
Read every page as a visitor would, looking for errors Check the site on several devices Ask a few people to use it and tell you what confused them Watch the error log
FIRST MONTH
Check Search Console for crawl errors Review what pages people actually visit Confirm backups are running Apply any updates released since launch
WHAT TO SET UP
Backups, verified A maintenance routine Someone responsible for updates
THE MOST COMMON OVERSIGHT
Nobody assigned to maintain it. Sites launch and are then untouched until something breaks.
Decide now who does what, and how often.