did you mean the amount of oils and butters you can add to your mp base? if so, i think the rule of thumb is 1t-1T per pound of soap. adding too much can interfere with suds afaik.
Danali,
Check the shelf life of any fixed/carrier oil you add. Grape seed has a short shelf life of approx. 6 months. Jojoba's shelf life is a lot longer -- about 2 years.