My limit is usually 40 minutes on a long run because I am bored, injured or just had enough. Today I ran 30 minutes out on a straight course and 28 minutes back the exact course. A beautiful day today no winds, 45 degrees and clean air. I was not even trying to push the pace just cruising. I am excited about this since I have not run that much in more than a couple of years. The real test is how I will feel tomorrow. I will keep you posted. You'll never know what you can do, stay persistent, pace, and take care of yourself (sleep, nutrition and exercise in moderation). Happy exercising to you, keep it up!