Thread:ClariS/@comment-24603390-20140919022108/@comment-24603390-20140919085609

Lifesteal and spellvamp are both used to restore health, the same as that of potions. To my knowledge there is nothing that scales with lifesteal/spellvamp its purpose is only to restore health. Lifesteal/spellvamp and potions both cost gold, and both restore health., and are therefore comparable. The difference between the two is that one has fixed healing, the other variable. All players wish to restore health, and all players should look to spend there gold efficiently. Potions restore ~4.3 health for  each 1 gold spent on them. For purely sustain purposes, for lifesteal to be a better choice than potions, it must restore more health than spending the equivalent gold on potions. The point where lifesteal becomes more efficient is after dealing 23,571 damage from basic attacks (and applicable on-hit effects). If you will deal more damage than this during the time of the game that you require sustain (usually the laning phase), lifesteal is a more efficient option.

Lifesteal/spellvamp is dependant your damage output, whereas potions are not. For this comparison to be useful, you must be dealing damage when you require the healing. (I think this is what you were meaning in your comments above.) So this comparision is most useful in the laning phase where you are normally constantly trading damage and then restoring it. During times of high damage output (such as dueling), lifesteal/spellvamp will heal at a rate faster than that of potions, making a more useful choice. During these times, this comparision is not as useful.

The purpose of the calculations are to determine when lifesteal/spellvamp becomes a better choice than health potions, so that players can make informed decisons about which to buy. It is meant to guide players, not command them.