Having just done two long trips – one of 6000 and the other 3000 miles – often with up to 8 hours driving per day, I have found the seats perfect!
With all the adjustments in the multi-contour seats, the only issue is after several hours and then I turn on the active seats which keeps me going for another hour or so.
Suggest you have the dealer check the seat alignment.
2013 650i Gran Coupe xdrive
Prior: 2010 550i GT xdrive | 2008 335i Convertible | 2007 335i Coupe | 2006 130i Hatch | 1998 540i Sedan