After a cystitis infection clears up, there can be a residual problem of urinary frequency. In other words, no cystitis pain or burning, but just a need to urinate rather more often than is comfortable or convenient.
When you need to urinate more frequently than is normal, the bladder doesn't not fill to capacity, and when this happens for an extended period, it begins to shrink. Similar to the way our stomachs expand or shrink if we over-eat, or fast. A shrunken bladder will not store the same amount of urine you had become used to, so you get the urge to empty it frequently. One way to counter this shrinking tendency is to resist the urge for a little longer each time you need to urinate. Over a few weeks, the time will vary for each individual, you should be able to restore your bladder to it's normal capacity.
While there is no scientific evidence to suggest supplements may help resolve urinary frequency problems, you may want to try a maintenance dose of D-Mannose, or taking a level teaspoon of Xylotene 2 - 4 times a day.