I think the answer to this is: it depends upon your personality and temperament, and secondly, on what your goals are.
If you are a very tolerant, patient person and you like being told what to do, you could pick a Cathe rotation from her rotations forum that focuses on either strength or endurance and follow it for the month, making notes weekly about how you feel, what response you are seeing, etc. Then the following month you could pick a rotation for the opposite trend, say you chose strength before, now you do endurance. Again, track how you feel, what changes you see.
At the end of this experiment, you can decide which brought about the most desirable, for you, changes in your body and fitness and dedicate more time to that particular mode of weight training. Bear in mind though, that after 6 weeks, your body will have adapted tp that type of training and you will need to introduce changes again to keep seeing fitness results.
Personally, I hate being told what to do, I have never done one of Cathe's rotations in my life and even if I write one out of my own, I end up changing things all the time because I do not like my workouts to be written in stone. So, the idea for me of doing, say, Power Hour three times this week on some endurance kick would send me running for the hills!
I am someone whose temperament dictates that I mix things up to avoid boredom.
There are no hard and fast rules that say you SHOULD do all endurance this week and all strength next week, or that you should follow endurance only for the next month and then swap to strength for a month. Certainly, if you are consistent and train with just strength for a month, for example, you will certainly see results. So, it depends again upon whether you have strong and firm goals and what those goals are.
Personally I do different types of training and I do all of them all the time, fitting them in after my cardio and varying which I do depending upon how much time I have left, how tired I am after the cardio, whether I ran or not, and whether I am working out at home or at the gym since each site offers different equipment. I do weight training as heavily as I can for the upper body since I find it hard to build muscle on the upper body and I have long, thin arms and no push up power to speak of. Then, I do mainly endurance training for the lower body. I also do specific weight/functional training moves that are designed to protect my knees and hips from the impact and forces involved in running. These moves include some pilates type moves, lots of stability ball work, resistance band work, etc. My weights work is, therefore, dictated by functionality rather than aesthetic goals. I don't lift to lose weight or gain muscle for the sake of it, but to protect.
So, what are your goals and what is your personality type? There are no "shoulds." There is only: what do you want from your fitness?
Clare