Traveling on the interstate can seem never-ending when headed to a faraway destination. What better way to take it easy than turning on the cruise control until you arrive? While that sounds like an ideal plan of action, the truth is cruising along at the same speed the whole time may not always be the best option—on the trip and in financial planning.  Retirement is also like a road trip and target-date mutual funds are the cruise control. The problem with cruise control and target-date mutual funds—timing is everything. You may hit the occasional snag and need to slow down. Or perhaps you get a late start and need to accelerate to reach your destination. Whichever is required, it is a good possibility that a target-date mutual fund cannot give you exactly what you need, when you need it.