That is an excellent way to grow them. Mine are all in 8" pots, and spend the winter out of the water. In Spring I will put them into deep trays, 6 to a tray, fill the tray with water, and feed them through the water, with well rotted cow manure.
They should be potted into fresh acid loving potting mix each year, and divided as required. They will put long feeding roots out into the water, but these can be trimmed back when you divide.
If you get very hot weather at bloom time, you can move the pots into the shade to protect the flowers.
Cheers, Jan in Australia