I believe the tubes that failed where earlier part numbers. Universal says they have the problem fixed(?). We only have about 250 hours on the screens so I don't have a lot of data to give you. If I owned the aircraft(Older) I would just put a new FMS, Nav display and maybe AHRS, and call it good. It does clean up the cockpit a bit and lower workload but some things do not play perfect together.
The prices are dropping on this technology so I would be in waiting mode if possible.