Is a sagging floor possibly detrimental?
I had to have a structural engineer take a look at my house before I closed on it.  I have a roughly 1" sag in the middle of left half of my house where a pole was removed.  According to the structural engineer this would not get any worse and is "safe", aside from any annoyance it causes.  Yours may be a different situation, so I'd recommend having someone come out and take a look.  I believe mine ran me about $450.00 for the consultation.  Money well spent to know I won't fall through my floor at night.