It’s not about how soon they can go abroad, they can literally travel back next day. The stamped and endorsed visa at POE acts like a GC for one year. It’s more about how long they can stay abroad. Any time they stay for more than 6 months, they will be scrutinized at POE. Frequent trips of more than six months may result in POE office recommending court proceeding for GC removal. People have stayed abroad for more than a year with reentry permit and come back successfully but after heavy scrutiny and at POE officer discretion. Its all about maintaining residence in the US not visiting.