I've done a some retrofitting, here is what little I know.
Programmed start- great if the lamps are turned on & off frequently, such as a hallway with a motion sensor controlling the lighting. Otherwise, a waste of money.
Parallel operation is my choice. One lamp goes out, the other remains lit. The energy savings will probably (S.W.A.G.) more than pay for any shortened lamp life. If the fixtures are installed in an area where they are frequently turned on & off, you should be using programmed start anyway.
Can't comment on brands, I only have access to Adcance.
As far as ballast failure is concerned, I believe the Advance ballasts come with a 5 year warranty.
I'd go with the 120/277 ballasts, cuts down on inventory & errors.
Looks like you will be saving a lot of money once all the ballasts are replaced.
Try this site for more info on ballasts http://www.advancetransformer.com/university/default.asp
[This message has been edited by Tom (edited 10-26-2003).]