A card in your wallet isn't going to "make sure you are doing the right things".
I don't say that to disparage the CA program. I am a Certified Arborist, and I absolutely know it adds significant value to my business. However,
I make sure I do the right things. I go to training to keep learning. At those trainings I get hours to apply to Certified Arborist recertification. I'd still go if I didn't need to because they make me a better professional.
The designation is a communication to clients. It should communicate to them 4 things:
1) You passed a test.
2) You have met the at least minimum employment experience requirements.
3) You have agreed to a
Code of Ethics (and it provides an avenue for them to "punish" you by reporting to ISA if you violate that code).
4) If you have been Certified for more than 3 years it says you have pursued the at least minimal amount of continuing education to maintain Certification.
Those last two should help you do the right things...but they aren't magic - you still have to make the right choices everyday.
I'd encourage you to just jump right in and apply for Certified Arborist. Buy the preparatory book. People who have been paying attention and who have gone to continuing education for a number of years generally don't have trouble passing the test after they go through the study guide. (I say that...but when I took the test, you had to pass each individual section. I did had retake the section on cabling/bracing because I didn't have experience in that, and didn't study well for it...had to drive 90 miles one way to take a 6 or 7 question test because of that!!!).
How long is it going to take? That depends on you and when you can take the test. If you get the book and it sounds like first grade reading because that is what your dad has taught you for the last 20-some years it will take no time. If you get the book and it is the first time you are hearing everything.....you might want to go through it a couple of times, get some other materials, and visit some seminars for a year or two before taking the test.
Good luck!