Hi, Mel—massive congratulations on meeting your goal! Well done.
Here’s my report from the field as someone who is using Beeminder to maintain rather than lose.
I’ve been tracking my weight with Beeminder since last November, purely out of interest (I’m heading toward menopause, and also making some fitness changes I hope will help me sail through the last half of my life—oh, the optimism; of course I’ll live to be a hundred!—feeling great and being able to do everything I want to do).
I have a “ceiling weight” that is higher than I expect normal daily fluctuations (including those after, say, a weekend trip in which I ate and drank to my heart’s content, etc.) to go, but not so high I can let my weight creep up very far before I get slapped on the hand. If you look at my graph, you’ll see that I’ve moved that “ceiling weight” around a bit, working to find the place that hits that sweet spot. I expect it will continue to move from time to time, depending on how my fitness and diet changes (and menopause) affect the weight I can reasonably maintain.
To TL;DR it:
— weighing daily and seeing that on a graph is rewarding, and keeps me in control
— setting a realistic “sweet spot” ceiling weight that allows for reasonable fluctuations but doesn’t let me creep up too high has been effective, and I haven’t needed additional goals on exercise and eating to help me stay mindful of my weight (though I do have an exercise goal, because I effing hate exercise 
)
— I use the tip @philip showed me here to make stepwise changes to the ceiling weight when appropriate
— I like having a distant goal date; for me, it reinforces the idea that it’s for life; mine’s set for some time in 2020; other goals have 2026 dates, and I wouldn’t mind it being even later
Good luck!