Here are some things I've learned, singing my first Traviata. (Any future or present Traviatas who read this: I hope you find something here that's helpful to you!):
-Violetta isn't necessarily harder than Gilda--the challenge is totally different (for me, anyway).
Every singer is going to find certain roles and pieces to be more difficult than others, so what I write here is based on my own experience. Anyway, I've found that as far as maintaining dramatic intensity and presence onstage for a long period of time, Violetta is more difficult. From a vocal standpoint, however, I find Gilda to be much more difficult. Violetta may be physically onstage for much longer than Gilda, but she isn't necessarily singing big arias or duets all the time, unlike Gilda. I liken this to the difference between running a sprint and running a marathon. During a sprint, you have to exert much more during a shorter period of time, and in a marathon, you're exerting yourself over a longer period of time. But not only are you not necessarily exerting yourself as hard as you are singing Gilda, but figuring out how to pace yourself during Violetta is the key to success in the role. Which leads me to my next point...
-Slow and steady (or at least adequately paced) wins the race.
In fact, pieces of feedback I've received throughout the preparation and rehearsal processes have been about where I can give less voice during Violetta--I've never been told to give more. Economy and smart pacing are what win this "vocal and dramatic marathon." :) On this note, the potential "vocal potholes" in the role are in the declamatory sections in Acts 2 and 3--it's very easily to give yourself too much vocally and emotionally in those sections. If you pace yourself carefully, though, you should be just fine. Act 1 isn't a challenge, in this particular respect. On another note, I read this past week about how challenging the role of Mother Courage is, in the Brecht play "Mother Courage and her Children," because she has to carry the show for two and a half hours. When I read that, I admit that I thought to myself, "...and she doesn't have to sing over an orchestra during that time!" :) (Also, cardio classes, or any other exercises that increase your endurance and stamina, will be important!)
-Give your wrists and knees extra love.
In Acts 2 (Scene 2--the party scene) and 3, you’ll be on your knees and wrists a lot during the rehearsal process. Violettas, take good care of them, and be judicious with how you use them. If you’re in a production in which you can wear knee pads under your costume, all the better.
-Be realistic with what you demand of yourself.
Keep in mind that even Violetta, for all her demands (and there are many!), is not expected to sing full out for more than 3 hours a day. Don’t demand of yourself to do more than that per day. Pace yourself throughout the rehearsal process, and mark when you can. You’ll need to sing full out for musical rehearsals, but you can mark during staging rehearsals, for example. Take advantage of that, and come up with a “vocal game plan”—when to mark and when not to. And obviously, do NOT sing the whole role full out the day before you perform the role!
-Granola bars can be a Violetta's best friend (seriously!)
This may be the most "stereotypical opera singer" thing I write in this post, but I've personally found things like granola bars to be especially useful. That, or any kind of food that can keep you energized and full over a 3 hour opera, without making you feel lethargic. This is another thing that will vary from singer to singer, finding what works for you. So long as you're able to have adequate sustenance throughout the show, that's what matters.
These are some observations from a knee-pad-wearing, granola-bar-eating, cardio-doing Violetta! :) Thanks again to the Jerusalem Lyric Opera Studio for the opportunity to sing my first Violetta!