Rules API is an option, in the time properties such as sleep you can use bigger units like Hour or Day. In the API documentation, you can see the syntax and in the posts below, there are some examples and the instructions to install a rule.
Using the Rules API is another good option, you just need to use an API test tool, like Postman.
The sample below has this workflow:
IF the button is pushed
THEN set a 30-minute timer to turn OFF the TV
"name":"If button is pushed, set timer to turn the TV off",
You can create your Rule Automation using either Postman or Insomnia. Personally, I’d suggest you to use Insomnia, as it has a simplier and intuitive UI to perform your API calls. Please, follow the steps below:
First, you must create a Personal Access Token that you’ll be using at your Requests Headers to the SmartThings API.
Then, you must get the list of your devices making a GET HTTP Request at the SmartThings Devies API and track your GE SmartSwitch’s Id.
Finally, update the JSON file from above with your GE SmartSwitch Id and make a POST Http Request to the Rules API.
I hope this information results useful to you.
Let me know if you have any questions.