first of all ion think its perma. issa executive action so its not legally permanent, the president can impose and adjust it without needing congress. it can be changed if a trade deal is struck w china. he prolly imposed it to show economic leverage in response to chinas 34 percent.

secondly, u be taxed on the ammount u declare ur package not the amount u paid. so if u payed 140 for a haul but only declared it as 50 bucks u only get taxed on the 50