When you hear this lady talk...

Citrus indoors year round at room temperature (which I guess is about 20°C) exposed to as much sunlight as possible.
The trees look good so I am wondering why I try to keep my citrus at 15 to 17°C :s.

http://www.youtube.com/watch?v=erJQynkg-ro

There is no way the trees in the video are living indoors. Those are most likely prop trees that are grown in a greenhouse and moved inside for the propose of the video. You could probably keep a tree alive and maybe fruiting if its the right variety. I would think lemons or limes would be the most suitable for indoors. They would not look like what you see in the video.

I was doubting myself. No dormancy doesn't seem very productive to me.

Tthe very optimum-ideal temperatures for citrus growth is between 73 to 86F (23 to 30C). Plus a two month cool rest during the winter which helps to set a strong bloom in the spring. - Millet