Cost. Meth. Specific and No. Series. Experiences?

Hy Everybody, is there anyone with experience about using the Item Costing Method “specific”? I’m worried about the creation of as many records of the Item Ledger Entry as every single quantity of Item to move. Due to No. Series use. How does the System react with this table with possible hundreds of thousands records? I clarify that i need to use this Costing Method to value my Inventory. Thank you in advance for your suggestions. Luca