What is the deal with sl_log_1.log_xid exceeding 2G?

I don't remember any mention in the slony docs of a maintenance 
procedure being required with regard to this.

I'm using Slony 1.1.0 with pg 7.4.6

Currently, the max value in our sl_log_1.log_xid is 2726870414

Q1) Have we already had potential wrap around and data loss? I don't see 
any duplicate key errors in slonlog on the master.

Q2) What is the maintenance procedure that needs to be run to prevent 
data loss? Can someone provide explicit steps that should be carried 
out? And at what frequency?

Many thanks

John