It seems like you have proven that 24 hours would be more than enough. I would change it to: "For a limited time, use * free for 24 hours", then inside the pro

It seems like you have proven that 24 hours would be more than enough. I would change it to: "For a limited time, use * free for 24 hours", then inside the product, push hard from them to pay, have a countdown somewhere very visible for when their license expires. it sounds annoying but I think it will increase your conversions tenfold.