How long can an EB-5 conditional green card holder remain abroad?

You should obtain a reentry permit if you intend to be outside the United States for more than a year. You must actually intend to live permanently in the United States and have ties to the United States in order not to be considered having abandoned your permanent residence in the United States. I would recommend that you consult your immigration attorney with any questions.

Use the 180 day calculation. A few days should not matter. Just be prepared upon arrival to explain any lengthy stay outside of the United States.

180 days is the standard for citizenship. Factual intent to abandon is the criteria in terms of losing the green card. Safest to apply for a reentry permit before departing if planning to be gone more than 180 days.

You may be found to have abandoned your permanent residency status if you remain outside of the United States for more than a year. However, being away for more than six months is usually okay as long as your reason for staying out does not show that your intent is to live outside of the United States rather than living in the United States permanently. The temporariness of your trips may depend on several factors, such as no permanent resident location in the United States, the reason for your trip and how long you intended to be absent from the United States, etc. More importantly, prolonged absence in conjunction with failing to file income tax returns while living outside of the United States for any period or declaring yourself a "nonimmigrant" on your U.S. tax returns, would lead to a finding of abandoning your green card status.

Stick with the days just to be sure. In fact, it is probably better to steer way clear of the 180 days. You are looking to obtain permanent residency. Be prepared to be here permanently.