What is the string size limit for a member property?

Can't seem to find it in any of the online docs.

For example, let's say I want to store related members (as a set in string
form) in a member property to be later retrieved as a set when aggregated
across members in a slowly changing dimension.

This was a method that Amir suggested in his paper on slowly changing
dimensions. However, a low limit to the size would make this impractical
(e.g. 255 chars doesn't go a long way when qualified member names get to 80+
characters and you're attempting to store member names...).

Neil Thomson