I don't know but last time I checked my plants we're pretty green and they reward me with these really nice little pearls all night long and I have four Milwaukee regulators. Never had a problem with them, never replaced the needle valve and one is four years old.
That being said, any regulator can break, many times it's by user error, but the Milwaukee, Azoo regulators work fine and are probably providing co2 to 1 in 3 tanks both for plants and calcium reactors on the dark side of the hobby.
It doesn't sound like you have a Milwaukee regulator, but just going by things you've heard. Saying a Milwaukee regulator is junk is like saying GM is junk compared to a Mercedes, but both will get you to work in the morning whether you have all the bells and whistles or not. So whether your regulator is a Milwaukee or a custom-built, dual stage, fuel-injected one they will both take you from 0 to 30ppm co2 on most days.
I have used and owned Milwaukee, JBJ, and Azoo combo setups before building my own. Out of the 3, I liked the Azoo the best, which I still have. While all 3 worked when I used them, the quality was lacking compared to higher end co2 setups. Back in my fluid dynamics course in college we took apart a pressure gage similar to the ones used on co2 regulators. The basic mechanics of one is simple. The increase in pressure is exerted on a small beam member. The force causes a deflection in the beam proportional to the pressure increase. The point on the beam member in the gage is connected to a spring coil that is attached to the needle one sees on the pressure gage. Most cheaper gages are made with cheaper materials, which may not model the proportionality correctly causing the gage pressure to be inaccurate. While this may not be vital to simply injecting co2 in your tank, I am using the explaination to show there is a difference in the engineering and manufacturing of co2 regulators, which includes the solenoids and needle valves that come with them. Light, co2, and nutrients all need to be in check for plants to grow. Not enough light then they really do not need the nutrients and co2 because they can not use them.
My point is that you personally may have not experienced problems with the Milaukee regulators, due to your tank parameters and setup. I personally have had issues with the cheaper regulator setups when I used them. I bought my co2 setups back in high school when I could not afford investing in more expensive ones. After building my own setups, I will not go back to cheaper setups. Just speaking from my own personal experience. Not saying that the cheaper ones will not work, but the quality and perforance of them will not compare to more expensive setups. In the long run, just pay more up front for better equipment.