This is one of the most annoying features I have found on the 4Runner. After I first got it, I would unlock the doors from inside and before I could walk out to the driveway to grab something they'd lock back on their own. I thought I was crazy for a while...then I realized that it's programmed to do that.
Who would design something like that??? I didn't push the unlock button for the heck of it...I meant to!
My Acura does the same thing, both my 4Runner and Ack do it, I believe both have a 60 second limit, I just don't unlock my vehicle, until I am within range that I will open the door before it relocks