Any excuse opens up another line of question.
If someone tells me that they have failed a ride because of only a few hours, my immediate question is why they took the ride in the first place; the message to me is poor judgement. We're paid for our judgement, not our monkey-skills at manipulating the airplane. The question here is whether one has the judgement to say he or she is not ready.
When a checkride is failed, it's rare that it's a single item. Frankly, if an applicant flies a perfect ride but makes one mistake, we do not fail them. When a clear pattern emerges and a mistake is made, that becomes the reason for the bust, but the fact is that the applicant will have numerous other reasons. It's the bigger picture.
If you failed a checkride due to a dirty window, there was certainly far more to the picture than a dirty window. It raises judgement questions again, but it's not just the window. It's not just landing 400' long. Remember that the underlying standard to all maneuvers and tasks is that the outcome be never seriously in doubt. Aeronautical Decision Making was added to the standard, along with scenario-based training to focus on the real world; these are the hallmarks that define a pilot.
The number of hours are irrelevant, except insofar as the regulatory requirements are met. Whether you fly one hour or ten or a hundred, you'll test when ready, especially if it's your call. When you work as a pilot, you'll be given limits to that. You'll be given a checkride or stage check and if you don't pass, you'll sometimes have one more shot, and you're done. I've represented a lot of pilots at hearings following training failures, and in many cases, there was some negotiation involved to get them the chance at another shot.
An airline or operator needs to know that their employees can take seriously the fate of the company and the flight and the passengers and the hundreds of millions of dollars that rest in each pilot's hands every time they enter the runway for takeoff. A failure of a line flight can change the direction of aviation. Colgan's failure certainly did, and that failure went back to numerous failures in the pilot's pasts.
Four failures do not change your fate, but you have got to take this a whole lot more seriously than you have in the past. You have got to establish a clean record in the future and show a solid employment history. You're going to have numerous checkrides, every few months for the remainder of your working life. Every one needs to be passed. You need to have an excellent track record.
Focus on that.