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The life cycles of stars especially in their formative stages varies greatly depending on the initial mass of the cloud which is undergoing contraction. A typical star like the Sun will spend anywhere from 20-30 million years contracting down to ZAMS (Zero Age Main Sequence). The protostar stage doesn't last all that long for solar mass stars and larger. Once contraction of the initial mass begins, it can occur very rapidly....10,000 to 100,000 years from the initial cloud down to the protostar. It's the next stage in the evolution of the star that takes the longest. The T-Tauri stage, which occurs in MS stars of 2 solar masses and less can take upto 100 million years and more, for the little M class stars. For a star of around 1 solar mass, the stage lasts 20-30 million years. Herbig Haro object are usually stars between 2-10 solar masses (B and A classes usually) and these object contract in periods from 100000 to 10 million years, depending on their initial mass. The larger of these stars have usually ignited core burning by the time they become visible and are actually still contracting down to their final radius as MS stars. Large stars, over 10 solar masses, form every quickly. A large 50-100 solar mass O class star will have contracted from gas cloud to ZAMS star in 50000 or less and have already ignited core burning long before they stop contracting to their final radius. Actually, their formation is not quite understood as there are problems with some of the kinematics of the contraction and the physics of the enormous energies involved. By rights, they should come close to not forming at all.
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