Are there any time-sensitive events in Skyrim, whose occurrence is based on how many in-game days have passed? Or, to phrase it another way, are there any disadvantages to waiting out time indefinitely, as is often suggested for merchant restocking?
The only time-sensitive event is your marriage ceremony.
Once you’ve proposed to your Future Significant Other, you’ll need to arrange the wedding.
After you’ve arrange the wedding, you have about 24 hours before the ceremony takes place (it always takes place between dawn and dusk, 6:00 AM – 6:00 PM).
However, if you do miss the ceremony, you can go to your Future Significant Other and ask for another chance.