valle locations

[WRGREENER]

ok the book tells me to tag and bag the valves and all the parts as i take it out. is this important if i am going to rebuild the heads (clean, m.blast, service guides, new springs, generally ready to accept valves (some new some old) since i will be lapping each valve (possible reworking valve seat if need) is it important to keep each valve in its original place or just good form?