I was reviewing my recent flights and see that my CHTs have been running around 300°F and even lower in cruise. About 60% power and LOP of course.   On a flight at 9000' cruise OAT of -2°F the temperatures were C1   C2   C3  C4  C5   C6 287 290 294 313 318 300  Avg 335 332 339 357 366 356 Max (in climb)   Is this too cold for extended cruise time say of two hour or so?