Quickbooks is sending invoices to some of my customers on its own! Some invoices are 3 years old.

I can see that this is important for you and your business, @tyrex1701. I'm here to ensure we get a resolution to these invoices sent on their own.

To begin with, you may check if the automatic emailing or recurring invoices are enabled. One way of sending invoices in bulk and at a later time is through batch action.

Here's how: 

1. Go to the Sales menu and select Invoices.
2. Mark the invoices you need to send.
3. Click the Batch actions button.
4. Choose to Send invoices.

After checking, if that's not the case, I'd suggest checking your Audit log. That way, you can verify if there's a user that initiated the sending of invoices that include the older ones.

Additionally, you might want to check this article and learn how to personalize and add specific info to your sales forms: Customize invoices, estimates, and sales receipts in QuickBooks Online.

I'm always here to back you up if you need additional assistance managing your invoices. Have a great day ahead!