You may be called upon to stand and play guitar, mandora or theorbo, archlute in any of various opera productions, so it is good to know how to do this and play from memory.
Also, if sing, you pretty much have to stand. An ultra light neck is very handy for this especially on theorbos, archlutes, and it of course makes a big difference when sitting down as well. All my big instruments have ultra light necks. dt To get on or off this list see list information at http://www.cs.dartmouth.edu/~wbc/lute-admin/index.html