ClearAll[Squeeze]
Squeeze[s_String,sq_String]:=StringReplace[s,x:(sq..):>sq]
s={
  "",
  "\"If I were two-faced, would I be wearing this one?\" --- Abraham Lincoln",
  "..1111111111111111111111111111111111111111111111111111111111111117777888",
  "I never give 'em hell, I just tell the truth, and they think it's hell. ",
  "                                                    --- Harry S Truman  "
};
Squeeze[s[[1]],""]
Squeeze[s[[2]],"-"]
Squeeze[s[[3]],"7"]
Squeeze[s[[4]],"."]
Squeeze[s[[5]]," "]
Squeeze[s[[5]],"-"]
Squeeze[s[[5]],"r"]