Yes Oreo Truffles do need to be refrigerated when not eating them within an hour or two.
Oreo Truffles contain cream cheese which is a perishable dairy product that goes bad when not kept refrigerated so for food safety and to keep the Oreo Truffles from going bad and making you sick or ill you should keep the Oreo Truffles refrigerated when not eating them.
Also when Oreo Truffles are kept out at room temperature they Oreo Truffles begin to soften as they sit out at room temperature which causes them to not be able to hold together.
When you keep the Oreo Truffles properly refrigerated they will last up to 4 weeks which is a month.
Usually though you'll eat the Oreo Truffles before then like I do because they are just too delicious and hard to resist.