A quick one (well, two actually)

hello
a quick question:
I cvsuped to current, did all that makeworld etc, and everything works perfectly :)
now,i want to add some options to kernel. There is no need to do all the "world" proccess again,right? (I did no cvsuping since then). It is ok to just  "make buildkernel" and installkernel, right? 
I'm pretty sure that is OK, since (correct me if I'm wrong,please) "world" process is needed when upgrading,right?

for the second question. every time I go upgrading my BSD system, entire "world" process is needed,no matter maybe a day passed since last cvsup-if I cvsup to newer, world is needed,right?

thanks!