@jackson_graves: Thanks for explaining your thoughts. Firstly, although it's debatable, I think a more accurate word-for-word translation is "I have gone to the beach" rather than "I have been to the beach". So for me it's a choice between "I have gone" and "I have been going".
I am happy with both of those provided there is something else in the sentence to provide the progressive/iterative aspect. While I would translate the unadorned sentence "Eu tenho ido à praia" solely as "I have been going to the beach", I would understand "Eu tenho ido à praia todos os dias desta semana" as either "I have gone to the beach every day this week" or "I have been going to the beach every day this week".
Well the portuguese "tenho + participle" always carries continuity and kind of an habit, a custom.
So, "have been going" is the best choice, and I would say only choice.
I understand that time adverbs can add the continuity part, and this makes the other choice acceptable, but even so, it doesn't carry the "habit/custom", it just says you went to the beach everyday.
Duolingo's team got fooled by the "word by word" translation, they should never had allowed that to pass through.
Is it perhaps better to understand this tense the same way as the difference between the verb aspect (something that does not exist in English but it does in Latin and most or perhaps all Slavic languages. The difference in the past tense between the verb aspects is that one is for one-time actions (the perfective aspect) and one is for actions happening either repeatedly or continously in the past (the imperfective aspect). It is sort of like the difference between the continuous and simple tense in English but not quite exactly the same and it seems like the Portuguese pretérito perfeito composto is perhaps better understood in terms of aspect (also that way I am less likely to confuse it with English present perfect since I would think about it in different categories...although it is still difficult not to do it because translated word by word it looks like present perfect).
Obviously, eventually you want to reach a point where you don't really think about it at all but it helps to put it into some categories in your brain when you're just starting.