ABS puzzler???

i have a 94 grand prix GTP , and some time during the summer the ABS came on after a few minutes of driving and upon the advice of some just left it be,now the past few nights it has stayed off a lot longer,last night ,early evening it stayed off for 15 minutes of driving,later that evening it stayed off for 25 minutes,on the way to work this morning it stayed off 35 minutes,on the way home it remained off for 45 minutes,does somebody have a hunch what is happening to the darn thing???????