How long does the gunite have to cure and how long does the plaster have to cure on a swimming pool?

Most recommendations for gunite are for a cure time of a week. While curing, the gunite should be wet down frequently, this will slow the curing and result in a stronger end product. I'm not familiar with the use of plaster in pool construction, so can't help you there...sorry.

As a pool builder, we let our gunite cure for 28 days as that is how long it takes a 12" x 12' bond beam to reach 80% of its strength.

For the plaster it depends on what type. Marcite and quartz application are applyed the pool is filled right away. For Pebble finishes, its applyed and then the next day its detailed and then filled. From there it takes a solid month keeping the total disolved solids (TDS) very low while the interior finish gives up moisture and calcium. During that time CYA, Salt and Calcium should stay out of the pool.

I would recommend 28 days as well with a drip line that keeps the gunite wet. The whole idea is curing and not drying. For plaster the appropriate method of curing is first to make sure the heater is bypassed and then keep the pH between 6.5 and 7 for the first month while the plaster cures. Brush daily. I would use a quart per 10,000 gallons of a good phosphate based sequestering agent at the initial start up followed by 5 oz per 10,000 gallons each week. Do not add salt or hardness for the first month. Bring pH up after the first month and then bring hardness up after the first two months. Add salt month three if it's salt water.