Dendrobiums like to dry out between watering. If it completely drys out in one day, you can water again the next day. What type of dendrobium is this? Some like a Shishir rest and do not require water or very little water throughout the season.
If you do not wish to water as often, you could repot your dendrobium in a mixture that would retain a bit of water. (Bark and charcoal mix) Dendrobiums like to be potted tight, so don't change the size of the pot unless absolutely necessary.