It depends of some factors, even if you set 0 fee (indeed in client says it is optional), there a times the transaction wont process if have no fee. Use to be when you have receive smalls transactions 0.000001 or so, and then yo want to send to another address, fees are expensives than amount to transfer.
I use to mine with p2pool, so I received ,lets say, 0.10 ltc every hour after a couple of weeks I transfers to btc-e and client wont do it unless I pay 4 ltc in fees. After this I've checked the transaction in blockeplorer and to transfer 40 ltc to btc use as origins more than 100 of the received, so the transaction size was 24 Kb or more, thats why it needs fee.
http://explorer.litecoin.net/tx/29a850f190bcce00b733a8093ec27b5601e0837e90a1e749d3eb42676ecf192cLook my transaction.
As I told you depends of size ot transaction, send 45 ltc with a "multiple origin" generate a transaction with high size, and this need to pay fees.
Regards