I wear my relaxed hair straight all year around, but I don't have the healthiest hair care practices, so I am always reluctant to give advice, lol. My hair is in fairly good condition though all things considered since I'm retaining length, with no breakage or split ends and it's between SL and APL. But it could be a lot better and I am working on improving.
I do use heat every day to maintain a straight look. I use a very low heat setting to minimize damage. At night, I want to say I wrap and moisturize daily and then cover with a plastic cap, but more often than not I fall asleep before doing all of that.
I don't have any creative styles. I usually just wear it straight with the ends bumped under or a ponytail with bumped under ends. Sometimes in a blue moon I will try a bun, but my buns are nothing special. I saw a woman with a very pretty french roll type style with curls on top using those little clamp things. It looked very simple, but I have no idea how she did it.
I wash and deep condition once a week and blowdry and flat iron on low settings, but I plan to try my hand at steaming and rollersetting. I get a retouch every 3 months and trim about a quarter to a half inch at that time.