Uncentered center bearing plate: The center bearing plate need not actually be in the center. It doesn't much matter where it is, since the purpose of the bracket is to anchor the spring ends. This anchoring must be secure, since all the torsion is held together at that point. On a stud-framed wall, this bracket may be placed over the stud closest to the center rather than exactly at the center of the door opening.
Dodging a falling door:: Reversing this equation gives us x=gt^2/2 as the fallen distance x for a given time t. How much time would you have to dodge a falling door if the spring were to suddenly break at the top of travel? Let us assume you are 5.5 feet tall, so the door will hit your head after falling 2 feet from its 7.5 foot fully-raised height. This 2-foot fall takes sqrt(2*2/32.2) = 0.35 seconds (350 milliseconds). The quickest human response time is about 200 milliseconds, so even if you are alert to the hazard, this leaves you only about 150 milliseconds to accelerate and move your noggin out of the way. If you are an Olympic gold medalist in the 100 meter dash, you can accelerate (horizontally) about 10 feet/second^2, and your 150 milliseconds of wide-eyed panic will move you all of 10*0.15^2/2 = 0.11 foot = 1.35 inch.
The "liability" angle: The flip side of "safety issue" is "liability". This is not used to directly sell you something; it is used to demean the cheaper alternative and prod you into buying a more expensive (and profitable) option. For example, you may be pressured into buying a whole new door, when you just need a new spring, by the salesman telling you he can't just replace the spring due to "liability" issues. Since product liability is a big burden on the garage door industry, and so many old doors (and especially automatic openers) are dangerous, this may be a genuine reason to accept a higher price.
Capable of lifting a seven-foot garage door up to 500 pounds in weight, the SilentMax 750 comes with a number of convenience features for automatic and remote use. The included wireless keypad and dual remote controls will ​insure that you are the only one that has access to the door. Compatible with a number of in-car remote systems like HomeLink, you can also keep the remotes at home if you are worried about losing the “keys.”​
Garage door manufacturers typically produce garage doors fitted with torsion springs that provide a minimum of 10,000 to 15,000 cycles and are guaranteed for three to seven years. One cycle is a single opening and closing sequence. Most manufacturers offer a 30,000 cycle spring. However, it is important to remember that if the weight of the garage door is increased by adding glass, additional insulation, or even several coats of paint, the life of the torsion spring may be greatly reduced. Additionally, springs at highly humid environments, such as coastal regions tend to have a significantly shorter cycle life, due to the corrosive cracking.