Mandarin: What happens when three 3rd tones occur consecutively?

Here's a brief explanation: https://en.wikipedia.org/wiki/Standard_Chinese_phonology#Third_tone_sandhi

我也很好 2+2+2+3

Or u can use third tone for 我 ang 也 if u want to mark subject and adverb, so

3 + 3 + 2 +3

I am a Taiwanese, I have never learned a saying of "If a 3rd tone is followed by a 3rd tone, the first 3rd tone becomes a 2nd tone (3+3 = 2+3)" before. But in short of one minute, I find what you say is reasonable because I do this way too. Then I check on Internet, and find what you say is totally true.
In your example of “我 很 好”, according to Chinese dictionary, all this three word shold be pronounced in 3rd tone. But if we pronounce all these thee words in 3rd tone, it sounds stiff and lack smooth and kindness feeling.
I myself, and I think, there're quite few like me, can’t not articulate all Chinese words meticulously, but it doesn’t prevent me from any kinds of communications. Just like, I know my English proficiency is so poor not only in writing, but more in pronunciation. But when I have chances to use English to speak to foreigners, they always say my English is good. To learn a second or third language is not easy. I do have a feeling, it’s more hard for a native English speaker to learn Chinese than a native Chinese speaker to learn English. Last, cheer for both of us.

I'm a Chinese. Long ago, I learned the tones. Maybe when I was 4 or 5 yrs old. Now I never care about the tones what you refered. I actually cannot distinguish the 2nd and 3rd tones. It's really very difficult, even for most Chinese. I never meet a foreigner, even a Chinese who can say Chinese with correct tones. While it never matters when we communicate. So forget about the tones unless you need to pass an exam. The most important for a language is communication. I can understand you; you can understand me. That's OK.