Can evacuated tubes be damaged from overheating

Can evacuated tubes be damaged from overheating

Hi does anyone know if evacuated tubes can be damaged if left disconnected on the roof for a year ,I have been told the panel was made by AMK  solar type opc but this one has 18 tubes it's 12 years old  the only ones I can find have 10 or 15 tubes do you know if they ever made an 18 tube version