Yosemite Mail.app – Rule stuck on 7 days

Mail doesn't really do out-of-office emails, because the application would have to be running to send a response. From Mail help:

Mail must be running to automatically reply to messages, because rules aren’t processed while your computer is shut down or you’re logged out. To set up automatic replies while you’re on vacation, ask your email service provider how to set up an out-of-office reply.

So, as the above says, you'll have to work with your email service provider to set up an out-of-office response.
If you post and tell us who your email provider is, we can help you set that up.

Please be aware that mail only applies rules to new messages. So deleting old messages may not work as expected, since the rule is checked once when the message is new the "date received" test fails. From the doc:

Rules are automatically applied to incoming messages, but you can apply a new or modified rule to selected messages you’ve already received.

You may apply rules to selected messages by:

Select the messages and then choose Message > Apply Rules.

You may be able to write an applescript to automate the last step.