Married for 36 years, Susan and Carter Hunnicutt of Milwaukee have been separated for the past six. They’ve been more than amicable. Susan, a freelance writer, lives in half of the duplex home they own. Carter, a musician and former fire captain, sends her half of his monthly pension and keeps her on his low-cost health plan. “We’ve been able to be cooperative,” says Carter, 61. Still, he characterizes their current agreement as “transitory.” Seeing that Carter has a girlfriend and sensing the ground starting to shift, Susan, 63, worries about how a divorce might affect her finances. So what should they do?