Welcome to the fourm! I jump around to alot of different fourms mainly palms and cycads and plumerias, but also love hibiscus. I have 3 hibiscus all in pots.

One of them Ive had for 3 years and I feel like its much more cold tolerant than any other tropical hibiscus. I took it inside 2 years ago because of how long it lasted in the fall and survived 2 frosts and a cool rainy fall with temps usually below 70.
It made it through most of the first winter inside with no problems, but then it had so many white flies that I couldnt control them anymore so in late march I took it outside and hoped it would stay above freezing. It didnt on 2 occasions and one of those occasions brought temperatures down to 25 degrees. It looked dead, every leaf was gone, but by may leaves slowly came back and by June it flowered with over 8 flowers on it per day on most days.
I brought it in again last year and it started to die around march at first slowly, but then rapidly so I brought it outside in early april as well as my croton which had a severe aphid problem and my lucky bamboo which also had some bug issues. A night got below freezing and both the croton and the lucky bamboo were toast, but the hibiscus made it through barely with the leaves tattered in the cold wind and rain we had the previous night.
So far this year it hasnt flowered, but looks far from dead, and actually full so we will see.

The second hibiscus I bought from a nursury this year even though it looked pretty pathetic. Now its still not a very full plant, but considering that, it does have very nice blooms with amazing flower colors which are peach and a red in the middle (its a double flowered hibiscus).

The last one was from a friend and has nearly doubled in size since last year, but is not a heavy flowerer yet which is okay because its still pretty little and has lots of buds.

Thats all the hibiscus I currently have. I dont have any pics of them yet, but if the rain ever stops maybe I can get some in!

Good luck