Any length attenuates signal. Adding 25' to your existing run will be fine with the quality barrel connection and protection from moisture.
It comes down to the quality and type of cable and connectors. If your coax is a good quality RG6 or the better grade RG11, distances of several hundred feet are possible without noticeable loss. I have installed fixed dishes with 300' of quad shield RG6 with little loss. Some fixed dish installs have used 500' of RG11 coax with good results. On the other hand, 100' of cheap RG59 cable can wipe out all but the strongest satellite signals.