After the domain expiration reminders which have been added earlier, you'll now be able to see the domain expiration date in your dashboard by hovering the scheme or domain (like for SSL certificate expiration):
The scheme will be orange if the domain is approaching expiration (<= 14 days) so you can more easily notice them, even if you did not enable the alerts.
Also a list of domain names expiring soon has been added at the top of the weekly report email, just below the list of SSL certificates expiring soon.
For the record, the domain expiration date is not updated frequently, because RDAP and WHOIS servers don't like this. By default it updates every 1000 uptime checks (so up to 1000h/41d if you have 1h interval checks). But this interval is greatly reduced (max 24h) when it's getting closer to expiration (15 days before), so you get more accurate warnings. Keep in mind it's possible to see an outdated value here, especially if the expiration date is far in the future. The time of the last update is shown in the popup.