Last year I hunted a ranch that was very flat and had few terrain variations for cover. I killed my buck at 621 yards, a doe at 454 yards and another at 379 yards.
The year prior, at another locale, I killed three... one was 120 yards and two were within 50 yards.
Terrain dictates. Both of these examples were kind of the extremes in my experiences.
For the most part, I would at least practice to 400 yards and limit shots to 300, unless you feel proficient beyond that. Watch that wind and get a good rangefinder...
Have fun!