You shouldn't experience any performance degradation with the longer cable. Cat 5 enhanced has a max length of about 90 meters.
Does the quality of the connection loose speed if the cable is further away from the modem right now I have a 3' cable but I want to use a 25' cable instead.
Will there be any problems using a longer type?
Or should I just put in a new phone jack to where the modem will be???