it is not the same, they are rather opposites. something with great sillage tends to have a high evaporation rate (but there are other factors), longevity means low evaporation rate. so, in general topnotes tend to have greater sillage than basenotes, but they evaporate faster. but then, i said there are other factors: some notes are more diffusive by nature than others. so you can have basenotes with good sillage, too.
spray more, and you will get both more sillage and longevity. but be aware about olfactory fatigue. spray too much, and everybody will think you have used too much, except you. you won't smell a thing anymore. never spray too close to your nose, as this will happen much quicker.