How long can milk products be frozen before spoiling? I made a sauce for macaroni and cheese about 6 months ago and froze the excess sauce. It is basically a bechamel sauce with a fair amount of cheese melted in. 

I realize that if I thaw and re-heat this sauce there may be taste or texture differences - the cheese may seize, etc. But I'm mostly concerned with whether this will be safe to eat. 

Is it possible for the sauce to have spoiled? If so, will reheating make it safe to eat or not?
Your sauce won't spoil when frozen, but the quality will decline. Not knowing how much time exactly there was between making it and it being totally frozen, there is a possibility that this is an issue. If it was chilled rather quickly, your sauce is safe to eat.