I try not to specify a burn in period as this could be construed as marketing bull or an excuse! I also probably don't have a unit with a 1000 hours on! As my rig kind of gets used for developments etc. and change things around on it.
This is an extract from a customer email which may help.
"In fact, the 500 hour mark is when the amp really shows its capabilities in soundstage, bass definition and dimensionality. At the 1000 hour mark the bass really comes together in terms of pitch, definition, slam and air. Low-end detail and impact has improved immensely --the difference between dropping a mallet on a spongy surface and a hard solid surface where the impact is not only heard but has a more visceral punch!"
"PS: it may be a help to new owners if you advise them that the amps do continue to "develop" beyond the 500 hour mark of continuous input through about 900 hours or so where patience is rewarded with exceptional sound quality at a price that defies convention. Truth be told, they really are quite good after a week of burn in!"