It can be. keep in mind, you must mostly reside in the USA. If you think that your LPR status cannot be deemed abandoned just because you have a reentry permit, you are wrong.
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Yes, it can be for multiple trips. You can stay abroad for extended periods. In the application, you must explain your permanent resident intention. Absences for over one year are also fine if you have a valid permit (but discuss the potential issues with an attorney). Secondly, keep in mind, the reentry permit serves to preserve permanent resident status but cannot be used to meet the requirements for naturalization. N-470 could help in that regard - if you are eligible.
Yes, a Reentry Permit is for multiple use and enables one to remain abroad for extended periods of time without "abandoning "his or her permanent residents in the US. A Reentry permit is valid for two years.
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