What I found is when sap is in it's liquid form it can be kept for 7 days at 38 degrees. This sap will freeze at the temperatures we are experiencing. My first batch of sap was a week and a half old and turned out great. I put it in the house for a day until it thawed out enough to detach from the bucket.
If I collect sap in the morning, it's always frozen at the beginning of the season. The bags are nice because they allow room for the sap to expand into ice.
If there is sugar in the ice, I won't be throwing it out. It takes a lot of work to set all this up for me. From what I could find in Maple syrup blogs, is there is sugar in it. There are conflicting findings as to what the sugar content there is from the thawed sap. So, does it depend on how fast it froze? Maybe when I'm more seasoned in making syrup, I will be more confident in what I do with the ice in the sap bags.