Yes, the heat of a car sitting out most times of the year in California gets an MRE in some cases over 120F for long periods of time. The end of life of the MRE is greatly manifold then, so you would need to cycle through them a lot.
Search out there, there is a graphical table out on the net which shows this.
"Just leave me alone, I know what to do." - Kimi Raikkonen
The moment the idea is admitted into society, that property is not as sacred as the laws of God, and that there is not a force of law and public justice to protect it, anarchy and tyranny commence.' and that `Property is surely a right of mankind as real as liberty.'
- John Adams