Consider yourself luck that you've been able to stay there this long - normally it's a year or so after you stop making payments. But like the others said, lenders have a huge backlog of homes in various stages of foreclosure so who knows when they will get to yours.
I wouldn't open up any can of worms by contacting your lender. Might as well stay as long as you can.
What I will say is that there is a process towards evicting you from the house. Whenever that day comes whether its tomorrow, next week, or next year, prepare yourself by beginning to build your credit back up and saving up some money to cover things like moving expenses and a security deposit on a rental. You'll most likely have at least 15-30 days after notice to get out of there, and they may even offer to give you a cash for keys offer if you keep up the home well and leave it clean and in good shape.
In the meantime enjoy the free rent and prepare for when that time comes. Good luck!