Fit at 40...how do I keep it that way?

I hit my goal weight at 40 (after losing about 60 pounds in about a year). I'm now 45 - I don't feel that I've had to work any harder or eat any less to maintain my current fitness level and weight. In fact, I think I watch my diet less and am more casual about workouts. I'm still consistent, but I've quit using a heartrate monitor/pushing hard and am pretty relaxed about eating.

I guess it's working - my doctor told me all my bloodwork looked better this month than it did three years ago (when I consider to be the peak of my focused effort of optimal eating/exercising effort). My weight is also stable.