Wouldn't we all like to learn 10-20 condensed techniques and then be able to "kick ass" in the streets?
The truth of the matter is that it is indeed better to practice 20 techniques 1,000 times than practicing 1,000 techniques only 20 times. So, your desire for learning the most effective 20 techniques is understandable.
However, nothing comes naturally in this world without practice. Perhaps 10 hours per week is too excessive for some, but I'd think that at the very minimum, one ought to practice two hours, twice a week (total of four hours) to keep existing techniques sharp while making improvements. Three times a week is even better. If three or four times a week is too tiring, for example, one can reduce the intensity level a bit. If it's a time problem, you can reduce other activities (less weight lifting or running, more Dojo time, etc.).
Really, once a week is not enough to make a progress, I think (kinda like lifting only once a week and expecting to become muscular).
Just my two bits.
For to win one hundred victories in one hundred battles is not the acme of skill. To subdue the enemy without fighting is the supreme excellence. Sun Tzu