If you make a splice the right way and consider the environment this splice might be exposed to, You can make a connection that just might out last the building. Think of it! If your have to splice in a humid or damp area then don't save the dielectric grease, use it! Or use the Twister's? By Ideal. They have the grease in them already.
My splices do fine,the ones i see that are bad are often in homes i never even wired.I recently checked that idea of letting the wire nut do the twisting.I will keep on pretwisting.