AX single compilation from AOT can take hours. around 4-10 hours.
depends on your server hardware specs.

but with ax build, you can boost up the compilation process because its using pararel compilation.

on MSDN : https://msdn.microsoft.com/en-us/library/dn528954.aspx

and this feature only works on AX 2012 R2 CU7 and above version.

example on command prompt (run as admin) :
cd C:\Program Files\Microsoft Dynamics AX\60\Server\MicrosoftDynamicsAX\bin

axbuild.exe xppcompileall /aos=01