I test my battery myself with a multimeter is that enough or do I need professional testing?

[simregistration]

I'm trying to save money and learn more about my car at the same time. I have a 2016 Toyota Camry and I bought a multimeter from the hardware store for about 40 dirhams. Every few months, I check my battery voltage with the car off. It usually reads around 12.4 to 12.6 volts. I also checked the voltage with the engine running and it reads around 14.2 volts, which I think means the alternator is charging. Based on these readings, I've been assuming my battery is healthy. But a friend told me that voltage testing is not enough and that I need professional load testing to really know the health of my battery. He sent me a link to khaleejarab.com/importance-of-regular-car-battery-testing-in-sharjah and told me to read about why regular professional testing is important. But I'm wondering is my multimeter testing actually good enough for a regular driver like me? If the voltage is good, doesn't that mean the battery is fine? What can a professional test tell me that my multimeter can't? I've heard that a battery can show good voltage but still has low CCA (cold cranking amps), which means it might fail when you need to start the engine. Is that true? Can a battery have 12.6 volts but still be too weak to start the car? How is that possible? If voltage isn't enough, what else should I be measuring? Is there a way to do a simple load test myself without buying expensive equipment? I've heard of testing by turning on the headlights and then starting the engine – if the lights dim a lot, the battery is weak. Is that a reliable method? Would that tell me more than just voltage? I don't mind paying for professional testing once a year, but I don't want to go to a shop every few months if my multimeter is giving me good information. What do other DIY car owners do? Is a multimeter enough for regular monitoring, or am I giving myself false confidence? Please share your experiences with home battery testing versus professional testing. What have you learned about what tests are actually useful? Any advice would be really appreciated because I want to be smart about maintenance without spending money on things I don't need. I just want to know if my battery is healthy enough to survive another Sharjah summer.