Me personally I usually cant go beyond sept, oct . My body is broken down big time after the hard and heavy training that goes on from right around the 1st of the year hard through the summer ... And truth be told once I come of the gear the pains that set in are just unbearable . To put it simply I think your body will let you know when to break . Just have to be smart enough to hear it and listen to it
I take a 5 days off every 6-10 weeks depending on the kind of training I'm doing.
It's important to take time off BEFORE your body is feeling rundown because you want to avoid a state where your body is regressing instead of progressing. I think it's much more effective to train right up to the borderline of being overtrained instead of actual overtraining.
When/how long to take time off is different for everyone. It takes experience and journal-ing. It depends on a lot of factors: calorie levels, training parameters (intensity, frequency, volume), age, general stress tolerance.
I agree that it varies for every lifter. Years of experience and training level make a huge difference. By training level I mean are you an elite level lifter or a beginner? If your body is at a peak level of development vs a beginner or intermediate level, time off is very different. In general, most lifters take too little time off, given our natural desire to make gains. For me, cycling into a less-intense form of training was always a way to give my body a break, and get ready for a long, intense cycle of high intensity lifting. Taking a week off once or twice a year at least does not seem excessive to me.
I train 5 days a week with an occasional week break or two all year round. I just cycle my workouts as to not put too much strain on my joints and ligaments, and to not over train.
I'm always changing reps, weight, super sets, tri sets, giant sets and volume, everything really. Not just to not hurt myself, but to keep it fresh and keep me interested and focused.
I try not to train more than 2 days in a row but if I do a 3rd it's an easier one. I train 4/wk. I go through different phases where I change intensity and weights used. I normally do 6-8 wk phases from heavy to drop sets & super sets. I don't generally take set times off and do not like to take more than 2 weeks at a time for holidays but would normally train at maintenance level as it takes too much time to get back into training.
It varies for everyone when to take a break but the diet plays a big part to your general recovery