When my children were born, we were told by our pediatrician to follow the schedule the kids set forth regarding eating. Your daughter will let you know when she is hungry. Trying to get her to eat when she is not hungry could set her up for problems down the road, as she may not recognize when she is full and could develop the tendency to over eat. At the age of five months, enjoy the time of peace and quiet while she is sleeping. That being said, make sure your daughter is gaining weight and growing as she should. If she is at the low end of the weight/length range for her age, she may need to be put on a schedule and be fed in the middle of the night. Generally if this happens, she will also be put on a high calorie formula as well.
As far as sleeping for so long, just try to set her down at a regular time every night, with as similar bedtime routine each night, so she gets used to a certain bed time. Children at five months old require a lot of sleep! Especially when she is going through a growth spurt. She should be getting around 15-17 hours of sleep every 24 hours. Some require more, but some require less. For the most part, at the age of five months, your daughter still gets to create her schedule and you and your husband are along for the ride. As she gets older, you will have more control over her sleep and eating schedules. Just enjoy the full night's rest!