Suspending Automatic Rebuilds
You can defer the update of assemblies until you are ready to rebuild
the assembly. By deferring the update, you can make many changes, then
rebuild the assembly once. The assembly still rebuilds automatically,
if necessary, for internal updates and to protect the integrity of the
model.
Use this option only when absolutely necessary.
Rebuild errors created while this option is active will not become apparent
until this option is deactivated (or you do a manual rebuild), which can
make it difficult to determine the cause of the errors.
To defer the update of assemblies:
Right-click the assembly name at the top of the FeatureManager design
tree, and select Suspend Automatic Rebuild.
(Rebuild Suspended) appears
in the status bar.
To manually update when in Suspend
Automatic Rebuild mode, click Rebuild 
on
the Standard toolbar.
To turn off the option, right-click the assembly name at the top of the
FeatureManager design tree, and clear Suspend
Automatic Rebuild.
You must reset the option every time you load the assembly document.