For the practitioners of any kind of skilled trade, there is going to be a part of your education which simply can not be done in the field. For some people (such as if you work in HVAC), it is your initial certification process. While for others the level of formal schooling you need is not nearly so intense, there is almost always going to be a time in a trades person’s career when they have got to hunker down in a class room, and listen to a teacher who will give them a few nuggets of insight that they might not have gotten on their own (or at least, not without some painful personal experience and observation).
For some people, this is a full on technical school in which they go from knowing how to turn a wrench all the way to being able to identify all kinds of arcane components, and be able to field strip a given type of system like a green beret can field strip his weapon (blindfolded and hanging upside down… if the situation ever called for it). The question you might be thinking about is, is it worth all of the money that this is going to cost?
If you are just going to get certified and do a few jobs a year while you primarily work at something else, absolutely not. While being technically trained is a very good thing for most people, if you are a lazy lout it is not going to work well for you at all. You have got to have the hunger to succeed, and be willing to go the distance to make the really good money. You are not guaranteed anything.