1) To maximize your time usage, I'd consider buying a few extra magazines and pre-loading them prior to starting the range session, so you don't have to waste as much valuable shooting time on filling mags (assuming that will help; sometimes it won't).
2) You might want to consider taking a smaller amount of ammo with you, so you don't feel pressured to shoot all of it in a single session. Better to shoot 50-100 precise, well-controlled shots than 150-200 willy-nilly shots which will reinforce bad habits, ultimately making these habits harder to overcome and reprogram. If you feel tired, or start to "throw" shots out of the groupings, don't require yourself to shoot the rest just because you paid for the range time. Leaving 10 minutes early with a strong finish is far better than shooting up to the last minute and "wasting" the last 10-20 rounds by using bad technique.
3) Being aware of the possible safety hazards in rushing is the first step. A truly responsible shooter will NEVER compromise safety for any reason short of a life-or-death defensive situation (which often can't be resolved using "range rules" and procedures, or so I'm told).
4) See #2. Quality, not quantity, is the watchword. I've only shot a few times on indoor ranges under similar constraints, so I can't directly compare my situation to yours, but on my local outdoor ranges, there are a host of other problems that can also cause similar time-related conflicts. Weather conditions (do you shoot until your hands are completely numb, or only halfway; how many warm-ups are too many?), calling range breaks to check targets (the guy that's shooting at 300 yards is always on MY relay, and he usually doesn't own a spotting scope, either, so I have to wait for him to drag his butt to the 300 yard target line, analyze his target, and wander back; takes up a LOT of time that could otherwise be used for shooting), and having a black-powder rifle shooter on the next bench (UPWIND of me; gotta love that recurring cloud of dense gray smoke). Short of having your own range, there is almost ALWAYS going to be SOME conflict with time, or other shooters infringing on your available time. Just try to make every shot count!
Who said "Practice doesn't make perfect; PERFECT practice makes perfect."? I mean, besides me...