I surrendered with DIY recharging. I'm just not confident it is healthy for my AC system. Those cans measure the low pressure side but not the high pressure side and both are important. Additionally, many of those cans add a sealant in their formula. Those sealants cause as many problems as they solve. It acts like cholesterol. Getting your AC system hooked up to professional manifold gauges that analyzes the entire system is a good PM decision. If it turns out there are issues they have all sorts of diagnostic equipment to find leaks. Boroscopes, dye, sound detection, etc... But I will also add this...there are a lot of crappy AC techs out there. They don't know crap. You have to ask questions to see if they know their stuff. Like what kind of leak detection they have. If they say they don't have boroscopes or sound detection then go elsewhere. Also, they have vacuum pumps to purge your AC system before recharging. Vitally important when recharging an AC system with issues. And if your charge is low then there's a reason for that and suggests there is an issue.
Here, I just dug up a video explaining it better than I can. This guy is a little on the nutty side but he's correct in what he's saying.
I love this guy, I've watched several of his videos and am always entertained.