A piano should be tuned 1-2 weeks after delivery.
A piano that has been moved and spent time in a truck may not be out of tune after it
is delivered. Pianos are tough and can withstand up to 20 tons of string tension and decades of heavy use, so moving usually has very little effect on the piano.
Steinway recommends 2 weeks and Bechstein 1 week after delivery. Remember the primary reason a piano goes out of tune is because of humidity changes.
New pianos will go out of tune sooner because the strings are new and still stretching,
this is why piano manufacturers recommend four tuning the first year.
A piano will always hold tune better when tuned by a skilled tuner, but stable temperature and relative humidity conditions will also increase the likelihood of good tuning stability.
