If you get enough orchids of varying types, you'll usually have at least one or two blooming at any given time
hehe
Sequential bloomers (some Phals, some Paphs most notably), and plants that hold blooms a long time (some Phals, Cyms, some types of Dens - I know that Dens from the Latouria section hold blooms 3-4 months, there are others as well), are also helpful to ensure always having SOMETHING blooming
Some can bloom multiple times a year when a bit older (mini and compact Catt hybrids, some Vanda alliance hybrids, some Oncidiums and Oncidium alliance hybrids)
Has worked for me, anyway - I don't have a particular focus on any specific type of orchid, so have a variety. Have gotten what I like that I think I can grow with my conditions, and usually have at least one or two blooming at any given time.