The more you tune your harp, the more it will stay in tune and the better your ear will be trained to hear when it needs tuning. If it is kept all the time in a consistent environment, it may not go much out of tune and may need only a little touch up tuning. Gut strings tend to be more susceptible to changes in humidity and temperature than nylon. Wire strings are usually the most stable.
That being said, one should make the best use of one’s time. If there is only an hour to practice, decide how much time you can spend on tuning and how much on practicing. Tuning can be a relaxing process to put you in the mood for practicing. As your ear improves, you may find it annoying to practice on a harp which is out of tune (depending on the individual). Maybe just fix the strings that bother you most at any given session. Harps don’t go out of tune uniformly, so if you don’t have perfect pitch, you may not know which are right: the ones which sound sharp or the ones which sound flatter than others. If it sounds mostly in tune with itself to you, that may be sufficient for practicing.