Generate a new package every day or week and include current date. Do not allow to update to package older than X. Synchronize time using one of the time signa

Generate a new package every day or week and include current date. Do not allow to update to package older than X. Synchronize time using one of the time signals available in the area or use signed channel for time sync. Using radio time signal it can be easy to spoof it if your location is known by the intruder, but makes it practically impossible for remote exploits. But radio signals may have bad reception inside a house.