The limit is not $500 per non-cash donation, it is a total of $500 for all non-cash donations. But I'm not sure why there would be a concern. Turbotax will automatically prepare form 8283 if your non-cash donations are more than $500, you don't have to do anything extra. And the requirement that you keep receipts and other documentation is exactly the same whether you donate more or less than $500 of total non-cash donations.
If your non-cash donations exceed $5000, you will definitely have additional requirements.
