I have had a set since 95 and love them.
The panels WILL need to be replaced at some point if they have not in the past already. I would ask.
There are also updated woofers available should you ever need them.
If you do need panels, a set will run you $700.
Ask how often the panels were vacuumed. Doing this regularly prolongs their life.
How much can you get them for if you don't mind me asking?
Is this your first set of electrostats?