just had the head machined flat because of overheating and blown head gasket. before i put the head back on, should i replace the valve stem seals? has anyone had to replace these seals before? how often are they needing replacing? or will i get many more years before they will worry me?

i am eager to put my car back together, but if they'll need to be replaced soon, then it would be a wise move to do it now.

the other concern of mine is that i have just had it all checked, but what if for some reason it doesnt go back together properly and there is a leak or something. Will it matter if the valve gets rotated.

thanks guys