I am a huge proponent of focused, efficient practice - the kind where in 20 minutes you can really solve problems and learn what you need to learn and move on with your day. I talk about that kind of practicing a lot when I teach, because no one ever has the time to actually do all the practicing in the world. But what is often overlooked in this conversation about directed practicing is the technique of just plain putting in the hours, and there is really no substitute for this.
I can learn the notes of a piece in a few minutes, to the level of not making audible mistakes in the orchestra. I can plan the phrasing of my solos in just a few minutes more, and sound like a smart and well-prepared musician. But what I can't do in just a few minutes is build up the strength and endurance of my embouchure, and have perfect control over my attacks and releases, and have the confidence that comes with a strong base of hard work under me. There's a comfort level on the instrument that comes from playing it all the time, and an hour a day is not sufficient.
Runners call this junk miles - running without a specific workout plan just to boost your weekly mileage. But averaging 20 miles a week instead of 10 really does make you stronger and set you up to add quality workouts without getting injured. When I was 10 months pregnant (or past my due date, anyway) I had three or four days worth of false labor. (They call it pre-labor now, to make it less discouraging, but I figure that if it doesn't result in a baby it doesn't REALLY count.) I would have contractions that increased in frequency and intensity for hours and then petered out and vanished. It was very very frustrating, but not actually useless. I dilated a good portion of the way while not actively suffering, and when real honest-to-god labor finally got started things went very quickly. My body had been practicing the process, and gradually building its base of work. Both of these paradigms apply to the oboe, clearly and directly.
I'm not talking about playing the instrument just arbitrarily, without good attention (while watching television, for example) but if I'm tired of the excerpts I'm supposed to be playing, or burned out on my concerto, I'll pull out something to sightread - a concerto for some other instrument, or an etude that I can transpose for the additional brain challenge. I can work on arpeggios or vibrato or intonation or really anything. Sometimes you need to just put in the hours.
I'm working myself back into the swing of things after Zoe's birth, and have been practicing a lot. But, as is inevitable with a newborn, I am frequently interrupted. I'm logging plenty of time, but in 20 or 25-minute segments interrupted by feedings and diaper changes and snuggles. And for 20 minutes at a time my playing is sounding pretty great. BUT a few nights ago I played a concert with a woodwind trio, and it was 45 or 50 minutes of baroque and classical trios - read: constant playing. By the end of the show I was really struggling to hold my face together and my goals had degenerated from making beautiful musical phrases to just making attacks and then to NOT making too much of an ass of myself. That's where putting in the hours really would have helped me. My recommendation to those working to bolster their endurance is very specific, and easy to describe but hard to do. Just play the instrument. When you get really tired, keep going and try to make a good sound or good slurs or whatever for just a few more minutes past the point of fatigue, and then put it away. Come back the next day and go a few minutes longer. It's not a shortcut or a quick fix. Just put in the hours.