With age comes wisdom. We've heard it for years, and it still rings true. With every day, week, month, and year you spend in the gym, you learn more and more of the finer details and bigger concepts which allow you to possess the knowledge needed to guide your training to take your physique to the highest level. Along the way, there are plenty of "ah-ha!" moments, when you realize some pre-conceived notion you've always held isn't true at all. It is through crushing these assumptions that we are able to stop getting in our own way, and at which point we finally realize our own physical potential
Only YOU are stopping you from fully reaching your own muscle development potential, and only YOU can stop this from happening. Let's look at your biceps training. For most lifters, biceps training isn't something they put a lot of thought into, right? They attack biceps day with heavy curls, and they curl until they cannot curls anymore. This usually take 15 to 40 minutes, as the lifter bounces between various free weights, machines, and cable options in the gym.
The motion is essentially the same. Sure, the weights might get lighter and the rep ranges may get a little higher as they move from "mass" to "toning" desired outcomes as the workout progresses, but the basics are the same. Mindless curling until the biceps muscles fail is essentially how most people in the gym see biceps curls.
You're an analytical lifter, so you never let the status quo with any muscle group dictate how you train in the gym. You think outside of the box, ever analyzing your training to determine what you have been doing wrong, even if you've been doing it for a long time. Biceps training is one such area where small mistakes can become established habits over time. Let's look at a few "rookie" biceps training mistakes that you may still be making.
Going too heavy, too soon
A common practice among nearly every lifter in the gym is a desire to start strong. You enter the gym, and your energy levels are at their highest. You are at your strongest point of the day, maybe even of the week, and you immediately want to start attacking those heavy weights. Despite your innate desire to crush the poundage, the fact your muscles are "cold" means they are vulnerable to injury. You should first take just a few minutes to warm up your muscles. Try performing a few sets with relatively light weights. This won't feel ideal for your ego, but it will warm up the muscles and loosen up the tendons. Your ego may take a brief hit, but the resulting blood flow and increased elasticity will make you even stronger when you finally decide to go "all out" with the heavy weights. You don't want to spend 8 weeks out of the gym because of a biceps tear or tendon issue. Start light for just a few sets, then go all out!
Maxing those weights
You're not a powerlifter, so you should never train like one. Sure, there are times when going for heavy on those bench presses can help spurn some serious new growth. But at the same time, your joints and tendons are doing the bulk of the work when you train with the 1, 2, or 5 repetition sets. This doesn't build muscle - it builds strength. Your goal isn't "biceps that can curl 200 pounds", you goal is to break 20 inches - or more - in upper arm measurement. This comes from activating the muscle fibers of the biceps using a repetition range of 8 to 12 repetitions per set and training in a slow and controlled manner, "feeling" each repetition.
Letting the cheating get out of control
There are always going to be times when you can get more out of your biceps training by using a little "Body English". Allowing the weight to swing just a bit can give you the ability to flex and tense and work the biceps even after the arms can no longer complete another safe and steady repetition using perfect form. This is known as "training beyond failure" with a little bit of cheating to make that possible. While it isn't something you should start your workouts with, it's a great way to wrap up your training day! Complete 8 to 10 reps with good form before ever resorting to cheating to burn things out.
We all know that the curl is the most simple, basic, and effective movement for targeting the biceps and helping those peaks to explode. However, they aren't the ONLY movement for upper arm growth. Mix things up with the use of spider curls, preacher curls, incline curls, hammer curls, reverse curls, and cable curls. See what creative biceps options the machines and stations at your gym have to offer. The motion of the lift will always be the same, but the angle can be as creative as you want to make it. Keep those biceps guessing, and they'll always be growing!
Neglecting the triceps
While this doesn't pertain to biceps training, per se, it should be noted that the triceps actually make up 3/5 of the mass of the upper arm. You can train your biceps until the cow come home, but if you're skipping triceps training, you are going to have some seriously small upper arms. Be sure to dedicate the same level of heavy, focused, intelligent training to the triceps as you are giving to your biceps. Develop both muscle groups of the upper arm, and you will maximize their overall development. Good luck!