Keep SSH Sessions Active, Or Reconnect?

Over on Slashdot user borjonx writes "Is it safer to log out of an SSH session, and re-establish it later, or just keep the connection open? Like many of you, I use OpenSSH to connect to my Slackware Linux boxes remotely from Linux and WinXP (putty.exe) clients. At home and at work, I wonder if it would be safer to just leave the connection open (my clients are physically secured, the servers limit connections with hosts.allow). Is it more secure to re-establish the connection over an insecure link (big bad internet) where people can sniff that handshaking, or is it more secure to just remain connected? I connect 1 to 4 times per day, most days."

Some folks answer that key-exchange is vulnerable, while others suggest that a persistent connection leaves you open to session hijacking. Still others offer that both are completely secure and you should use whatever method works best for you. What do you think?