I see too many people do this. They pamper and the baby the car for the break in period then as soon as they hit 1001 miles they ride the car hard. That is not good! It should be gradual, give it more rpm's and let the motor settle in at higher revs before driving hard. That's why during the break in period I periodically revved it to about 5-5.5k and then dropped it down to 4k. That way when it's broken in it's ready to go.
You've been running your car under 4k now for a 1000 miles and that's what the motor is used to, it hasn't run hard yet. I would recommend gradually revving to higher rpm's before going hard.
Of course that's just my opinion and this topic has been discussed to death on here with everybody having their own opinions.
Think of it this way... Say you wake up in the morning and jog 2 miles everyday, you're body's lungs, heart and muscles get used to this daily task. Now let's say that after doing this for 2 straight months you decided to get up and run at full speed. Well your heart, lungs and muscles are going...whoa what the hell is going on here, I'm not used to this, and they can't keep up. You run out of breath, you heart pumps hard and your muscles hurt. It's almost the same with a motor. Parts that are not used to going fast are suddendly pushed hard and they haven't been tuned to that yet, so they could get stressed. I don't think it will do any damage but it "could" shortened the life of certain parts.
They say within the first 50 miles your rings are as seated as they ever will be. I'd still be careful, don't gun it every single chance you get. But, you don't have to worry about constant speed or any of that bs.