Don't let the title of this post deceive you. If you have all the time in the world to train, full body workouts might still be the best way for you to train.
One big mistake I see people making when it comes to working out, is splitting up their body parts and training like your typical body builder does. What works for a genetic lottery ticket winner on steroids won't work for the regular guy, with a real job, and who's not a walking pharmaceutical billboard.
When I first started training with weights, I also made this mistake. This was back when I was 13 years old. Long before the internet. The only resources I had then were, unfortunately, body building magazines.
Although they did motivate me to train my ass off (I wanted to be a mass monster back then), I made modest gains at best. I can recall being at the gym for over three hours doing every exercise I imaginable for one or two muscle groups. A workout back then looked something like this:
Leg Day:
4 sets of Squats
4 sets of Hack Squats
4 sets of Leg Presses
4 sets of Leg Extensions
4 sets of Lying Leg Curls
4 sets of Calves
This was performed after training shoulders the exact same way.
I could write a small book on why this is ridiculous but I'll save you the time by giving you just two reasons.
Cortisol and Recovery.
Training any longer than an hour is a waste of your time from a hormonal perspective. Cortisol, a stress hormone, gets elevated as you train (exercise is stress). So you want your workouts to be brief and intense. Get in and get out and start the recovery process.
Training the way I did in the above example, would take to long to recover, thus keeping you from making big gains. You'd be forced to rest those muscles to long, so they would start to atrophy or shrink. One step forward, one step backward = getting nowhere.
Full body workouts lasting no longer than an hour will keep the volume down, allowing you to recover faster so you can train again. Even though you're probably doing a lot less volume than you're used to; don't worry. By the end of the week the volume will be about the same.
Since we learn better by application, let me give you an example.
You train your legs every monday and you do 12 total sets for them.
You switch to full body workouts and pick one exercise for legs that gives you the biggest bang for your buck, and do four sets. You do this on monday, wednesday, and friday.
By the end of the week, you performed 12 total sets for legs. The same as doing all 12 sets in one day.
The difference is you don't destroy your legs from doing all the sets on just one day, they recover easily, allowing you to train them more often. They get bigger and stronger because of the law of repeated efforts. Just like learning a foreign language would require more exposure, so will getting bigger and stronger.
Here's the workout I did yesterday with my good friend Ben.
A1: Back Squats: 4 sets of 6 reps with a two-second pause in the bottom position (disadvantageous position)
A2: Dips: 4 sets of 6 reps with a three second eccentric
A3: Neutral Grip Pull-Ups: 4 sets of 6 reps with a 25 lb. weight vest on.
B: Prowler Push; Low End: 3 sets of 20 yards.
So the A's were performed in a circuit fashion, hence the numbers after the A. We rested the amount of time it took for each of us to do each set, which was roughly 30 seconds.
This took probably 40 minutes tops.