my understanding is that it varies by surgeon. however, this is misleading. it doesn't just vary by surgeon it varies by patient and method of surgery. and, everyone heals differently and has different underlying tissue extensibility. i've head stories of surgeons (but can't verify the truth of said stories) that say they specifically move the hip as far as they can before it feels like it will pop out while the pt is still on the table; solid hips get less time on precautions and loose ones more. i've seen pts that dislocated and have precautions for the rest of their lives. if you feel confident you can assess passive accessory movement and see what it feels like but most PTs i know would never want to do that.

Some literature references:
A review (which I have not read) in 2009 states, "Available studies justify no hip restrictions following an anterolateral approach but none have examined the question for a posterior approach."
Sharma V et al. Clin Orthop Relat Res. 2009 Jun;467(6):1400-11.

"Total hip arthroplasty through an anterolateral approach is likely to be associated with a low dislocation rate. Removal of several restrictions did not increase the prevalence of dislocation following primary hip arthroplasty at our institution. However, it did promote substantially lower costs and was associated with a higher level of patient satisfaction as patients achieved a faster return to daily functions in the early postoperative period."
Peak EL et al. J Bone Joint Surg Am. 2005 Feb;87(2):247-53.