[Samba] Exceeding 200 client connections - samba 3.5.4 and squid

[Sean B]

Hi, 
We have a central pair of squid proxy servers running Samba Version 3.5.4-0.83.el5_7.2, on CentOS 5.4, which are using NTLM authentication for a number of trusted domains over WAN connections (all 100Mbit fibre links, so shouldn't be considered slow). Recently we've noticed that the winbind connections are exceeding the default 200, as below,
[2013/04/16 10:19:15.510056,  0] winbindd/winbindd.c:914(winbindd_listen_fde_handler)  winbindd: Exceeding 200 client connections, no idle connection found[2013/04/16 10:19:15.548416,  0] winbindd/winbindd.c:914(winbindd_listen_fde_handler)  winbindd: Exceeding 200 client connections, no idle connection found[2013/04/16 10:19:15.548545,  0] winbindd/winbindd.c:914(winbindd_listen_fde_handler)
I've read a fair number of the posts from a years ago on here, putting similar issues down to a bug with was fixed in 3.0.25, so I would assume this won't be affecting the version we're running and that it's possible our servers are in fact genuinely exceeding 200 client connections. There's possibly about 4,000 clients on the network at any given time.
I have a few questions which I was hoping someone would be able to help me answer,
1) Is there a way to monitor the number of winbind client connections in use?
2) will this version of samba allow me to increase this using the winbind max clients option in the smb.conf?
3) would it be recommend to upgrade to a newer version completely?
Thanks in advance, all input is appreciated,
Sean