The time of your workouts and timing of your workouts can have multiple variations depending on your current situation, exercise routine, goals and so on. The one thing of course you should make sure when working out is making the most of the time. Its one thing spending 2 hours at the gym, but its another when you spend half of that time walking around, talking to others, being on your phone and barely breaking a sweat. At the end of it, it all comes down to intensity and focus to ensure optimal performance and gains.
Long Workouts at the Gym could be your downfall.
The saying 'too much of a good thing' speaks volumes when related to exercise. Especially if you are bodybuilding or strength training. You need to know when enough is enough, there's only so much you can do to generate progression. Your body needs to rest from intense workouts. From the micro tears of your muscle fibres, exhaustion of the immune system and potentially high cortisol levels it is crucial to your progression & health to give the rest your body needs. The gaining of muscle tissue (Hypertrophy) actually comes from the recovery and building of new tissue. If you do not give your muscles the rest to rebuild, then potential gain will be eliminated. Same goes for you immune system. After a heavy strength training session, your immune system can be down for as long as 72 hours if the appropriate rest and influx of nutrients are not met. This can cause fatigue, leading to a drop in motivation and being susceptible to illness a lot more frequently. All in all doing more harm than good with detrimental effects on performance and putting you one step forward with 2 steps back.Be smart, don't be that guy who never allows his body to recover. More is not always better, so listen to your body and clever in your approach to building muscle.
Timing your Rest Periods.
Depending on what style of training you are performing or what goal you are training for ultimately determines the rest periods you need
Strength Training (1-5 Reps)
For strength training you want to be resting anywhere from 3-5 minutes during each set. This is crucial to getting your best performance from each set and allowing your anaerobic ATP-CP system to recover and replenish its energy source. Keeping your timings consistent through each rest period is important, if you allow variation in your rest periods it will have an effect on your true progression and give you false assumptions of your progress. I go into this a little in the Progressive overload article.
Hypertrophy Training (6-12 Reps)
The best rest period for this training style is 1-2 minutes. During your 6-12 reps you draw energy from the ATP-CP system glycolic system. The Glycolic system gets most of its energy from the carbs you eat. So unlike strength training when the dominant energy system is ATP-PC, you now have a second system to help you out. This allows you to recover quicker and replenish energy faster. They call this set range 'Hypertrophy training' because it is thought to produce the greatest muscle gain in combination with its suggested rest periods. It is a never ending discussion throughout the bodybuilding industry with ongoing experiments and studies bringing out new data all the time. My opinion is to mix a combination of rep ranges to ensure all energy systems and muscle fibres are hit. The Y3T Training protocol that was constructed by the incredible retired body builder and pro trainer to Flex Lewis, William Bonac and many more really hits this home.
Endurance Training (15-20 Reps)
For best results it is said to rest for 45 seconds to 2 minutes. This style of training is aimed at making your muscles more resistant to fatigue. The main cause of fatigue in endurance activities is lactic acid build up. Training at this level consistently with lifting weights in a 15-20 rep range will make your body more efficient at clearing lactic acid from the muscles. Lactic acid needs oxygen to help flush it away, when training endurance, you will increase your V02 max and cardio vascular system to generate greater oxygen and blood flow throughout the body and muscles therefor creating a more efficient machine to cope with lactic acid.
Remember to keep consistent at the gym, allow your body to rest when needed, incorperate progressive overload and you won't go far wrong.