Rules of thumb are only useful for typical and predictable situations.. The real answer depends on WAY more than the information in your question. Are you using compressors with turndown capability, are they recip or rotary (I don't have a feel for liters). What is the peak instantaneous demand of air, for what duration so you can size tank for the worst case drawdown. Etc etc
Real world knowledge doesn't fall out of the sky on a parachute, but rather is gained in small increments during moments of panic or curiosity.