Just some quick notes building -CURRENT / HEAD (FreeBSD 11).

/etc/src.conf

MALLOC_PRODUCTION=yes
WITHOUT_DEBUG_FILES=1
WITHOUT_LIB32=1

Disables debugging code in malloc, building (and installing) of debug files and also doesn't build 32-bit libs which you most likely doesn't need as you are compiling apps natively (64-bit) anyway.

/etc/make.conf

CPUTYPE?=nehalem
WITHOUT_DEBUG=YES
MK_PROFILE=no

Set CPU type, gives a nice little speed boost. Do not use native, it will break things (tm).
If unsure which model suits your CPU best read /usr/src/share/examples/etc/make.conf if unsure use core2.
Disable more debugging code and addtional files and don't add profiling data.

Following the regular procedure you might want to use these switches to automatically remove old files.

make -DBATCH_DELETE_OLD_FILES delete-old
make -DBATCH_DELETE_OLD_FILES delete-old-libs