If you see a lot of time spent in
resolving the target platform, you can set up some p2 mirrors on
local filesystem and enable them for Tycho via settings.xml. See
http://wiki.eclipse.org/Tycho/Target_Platform/Authentication_and_Mirrors.
It would replace all remote access to Nexus proxy by a filesystem
access, so it can save a lot of time.
For JBoss Tools, we also set up the concept of "unified" target
platform which avoids referencing too many sites from the target
platform. This unified target platform aggregate all the content
of the various sites we need, and put them in a single location.
Having a single location makes dependency resolution a bit faster.
Those possible improvements to target-platforms are explained
here:
http://www.slideshare.net/mickaelistria/a-journey-with-target-platforms
.
But there may be some other time-consuming operations. You'll need
to actually look at how build happens and find which operations
that the most time to figure out what can be improved.
HTH