Repot when new growth is 2-3 inches tall. Mature plants should not fully dry out. Improper humidity can cause bud drop. Use pebble trays where possible. Do not use fertilizers containing urea on orchids, because urea requires breakdown by soil microbes that aren't generally in orchid media.
Toxic salts can build up and damage roots.
You should use both inorganic and organic fertilizers, and alternate your brands of inorganic fertilizers regularly to offer your plants the widest possible array of trace nutrients. To prepare your own organic fertilizers, place about 3 handfuls of poultry manure in a 3-5 gallon bucket. Fill with water and allow to stand 2-4 weeks, occasionally giving it a stir. It is ready to use when it loses its cloudy appearance. Strain through muslin or other cloth and add water until it is a very light brown.