The way I look at it, you can push past your ordinary daily soft limit in this area, but there will be a cost, and the more you disrupt your routine in pursuit of your goals, the higher that cost will be-- past a certain point (likely different for everyone), you will get diminishing returns & risk of a breakdown goes up.

The balance to strike here, I think, is to give your mind & body a chance to recuperate before you get too close to that breaking point. Or phrased another way, look at 'pushing yourself into a second wind' as a critical tool for certain situations, but one to be used sparingly (preferably when you have some open calendar spots ahead).