Good topic : )
I think there are lots of differents kinds of concentration though, for example concentrating on one thought and deducing ideas in a more linear fashion is a lot easier than purposely deducing ideas while consciously opening up new topics as you are doing so, slowly adding them into the fold and taking them as inspiration towards deducing the original train of thought. An example of why the latter might be more difficult is that it is simply easier to become lost in the other ideas as they flood in, so one has to have a great deal of concentration, otherwise too many ideas could come in at once and one couldn't wade through them while staying focuses and also might run the risk of them digressing and deducing onto a separate matter. So, I think there are lots of different ways to concentrate and to that effect, that there are--therefore--many type of concentration in which to master not just 'concentration' ohh, as some vague term that applies to every situation. Regardless : )
In my eyes, I don't think one can ever reach a maximum level of concentration. The only way that could possibly happen is if the train of thought was so precise and able to encompass so many things at once that brilliant ideas would appear one after another after another. Lastly, we would be forgetting that alot of times concentration is broken not because one cannot think for long periods of times, but a thought may cross the mind that if one pursues or considers may put that person at risk of violating some moral code or idea that is also in place by thinking as such. Thus, the only way to aviod this would to be to have no moral code, or similar thought that effected the mind in such a manner, as to be able to continuously think deeper and deeper without breaking the train of thought. But other ideas arise, again, such as, can one really be considering to concetrate if one has the conscious effort to stop? Doesn't this mean that the idea of stopping is in the mind, thus actually preventing concentration in some other regard from fully happening? (remember there are multiple kinds of concentration). Even more, back to the previous idea of moral interference etc., if one had no interference then would this mean that no ideas were in conflict and if that is the case, would that already mean that one has already figured everything out in order to be in a state of no conflicting ideas? (i.e. there is nothing left to figure out thus no need to concentrate anymore)
But, I try to make an effort to concentrate pretty well with different kinds of thinking, and also sometimes force myself to do so under rough conditions to help me better when I am not under such pressure, also is one never under any pressure from some source in life at any moment? hmm, anyways : ) Who knows how good I am on some scale, but I would gander to say I am better than most when I take what I have gathered and finally apply it, but I'd say more of my time is done experimenting while trying to concentrate at the same time--it should be something to consider, about how much can one experiment with while focusing on concetration building and still have growth in both areas occur? Is there a efficiency curve of best ratio with these two functions? Lots more ideas, but perhaps that's enough for now ^_^