Requirement for splicing neutrals in a switch
If your splices are failing, that is a technique problem.  A competent wire-nut splice should be reliable. 

It doesn't matter legally, you can either leave zero spare length, 18" of spare length so you can splice to it if needed, or actually fit a splice.  You always have the option of running a replacement wire if needed since it's conduit -- that's why it's legal.