Organometallic compounds are deactivated similar to sodium or potassium. The reaction conditions have to be adjusted to the reactivity. The reaction is slower with higher and especially with tertiary alcohols. You may also slow down the speed by adding an inert solvent.
In contact with air n-butyllithium may ignite spontaneously! It depends on the concentration if this happens or not. Often a 15 % solution in hexane is used. This solution does not tend to ignite spontaneously. But be aware that the solvent may evaporate and the residue then may have a higher concentration of the n-buthyllithium.
n-Butyllithium slowly decomposes to lithium hydride which is also highly reactive and occurs as a white precipitate. But more often a preciptation is caused by lithium hydroxide which has been formed by a reaction of the n-Butyllithium with air moisture. With increasing precipitation the color of the solution changes from yellow to colourless. The supernatant liquid can still be used after the concentration has been checked by titration of a hydrolized aliqout.
n-Butyllithium may be disposed in a separate bottle. A deactivation as described below will yield products which will save money on disposing them.
Check every reaction in a tentative experiment before you allow a reaction of all of the compound.
Solutions with concentrations <= 2 molar may be decomposed by dropping them slowly into water. Very old solutions may even be poured into water. Higher concentrated solution may be diluted with hexane, but you should reflect, if this is meaningful since this will increase the amount of waste. With open bottles the solvent should not boil when it is mixed with water. The precipitation of lithium hydroxide may be dissolved with hydrochloric acid. At the same time the mixture is neutralized. The aqueous layer is flushed down the drain and the organic layer is disposed as solvent waste.