Hi @AKemple,
Historically, I think, this is not possible.
Going forward, here’s what you could do if you have access to workflows (available in Professional subscriptions).
First, create a property Number of sales activities leading up to deal creation. Then create a contact-based workflow. This workflow enrolls contacts when their Lifecycle stage is any of Opportunity. (This is automatically set when a deal is created for a contact.) Now, for the last step, simply use the ‘Copy property value’ action and copy the value from Number of sales activities to Number of sales activities leading up to deal creation.
By doing that, you’re freezing that number in a new property where it doesn’t keep on counting up. You can use it for reporting.
Best regards!