Five.  The number is five.  In my estimation, pianos require 5 tunings to stabilize the stretch in the steel.  Did you just read correctly? There’s stretch in steel? Absolutely.  And to prove it, try tuning a piano with new strings.  The first 3 times are almost laughable how much the pitch alters.  By the fourth and fifth times the strings level out.  Why is this important? There are three applications: if you have purchased a new piano, expect to tune it more than once in your first year.  Second, if you have just restored an old vintage piano – same thing applies.  I would hope that some of (if not most) of those tunings would’ve been done prior to arriving at your house but you’d be surprised at how off pitch i’ve seen new (and even expensive) pianos after the first year.  Third, if you EVER have a string break on a piano – just remember that putting the string on is the easy part… retuning 5 times that year… more challenging.  Recently i was at a customer’s home where the family piano had been dropped by movers.  6 strings broke trying to bring it back up to pitch – apparently the sudden jolt altered it considerably.  After ordering these new bass strings, it only took me a half hour to put them on but i told this teacher that i need to stop in for just a few minutes to tune because they won’t hold for the first few tunings. Just some thoughts to remember…