Is it normal practice to use 25 degrees of flaps when taking off at max weight in a PA-28-181?
The PA-28-181 POH I have read says to set first stage of flap (10 degrees) for a normal takeoff, and 2 stages (25 degrees) for a short or soft field takeoff. I've flown PA-28s quite a bit and I've never heard any suggestion of using 25 degrees for a normal takeoff. At maximum weight on a hot day at sea level 5,503ft should be plenty at 10 degrees, even if you are at 4000 ft pressure altitude it should still be sufficient, so I see no reason to set 25 degrees. 

Setting 25 degrees for takeoff increases lift at the cost of drag, and risk as you are closer to performance limits. An engine failure on takeoff with 25 degrees of flap will give you less time to get the nose down, and stall characteristics are harsher with more flap. 

If the runway was shorter I would see 25 degrees as good advice. There are plenty of light aircraft pilots who don't do performance calculations before they fly, drilling 25 degrees of flap when heavy into them may just save their bacon on a hot day on a short airfield.