Obama and Time Horizons

It seems that Obama is not the only person who wants to see a timetable for troop withdrawals from Iraq, it seems the Iraqi government wants one too. In fact I believe that this is not the first time that the Iraqi's have stated that they want US troops to leave. Now Bush is talking about a "time horizon" for withdrawals. Like most people I'm wondering what a time horizon is. I believe it is just playing with words. When one is looking to see when the sun will rise or set on the horizon you consult a timetable. So lets just call it what it is, a timetable for withdrawal.
The problem for Bush and McCain is that they have painted themselves into the corner by saying that withdrawing troops is losing. They are trying to have it both ways by saying that the surge has reduced violence in Iraq but to withdraw would put the surge in danger of failing. Bush and McCain have never defined what success would look like. I believe that Obama is correct when he says " Bush and McCain have no plan for success in Iraq only a plan to stay in Iraq". Why else would McCain be willing to stay in Iraq for 100 years.