Q.growing orchids
How long should an orchid bloom last and how long between blooming?

How long the blooms last will vary from the variety and the environmental conditions that your plant is growing in.
Optimize the Orchids care, humidity, light conditions, watering and planting medium and you can enjoy Orchid flowers for many weeks and in some cases months.
Following blooming most Orchid plants need a dormancy period.
https://www.gardeningknowhow.com/ornamental/flowers/orchids/indoor-orchid-care.htm