I have a Watchguard XTM22 that has tunnels setup to a Netear Firewall and other Watchguard X20e etc. One tunnel goes to a Draytek 2820 that once a day will disconnect, it is almost like it just times out. The tunnel can be connected again by simply starting a ping from the Wathchguard XTM network to the Draytek. I have changed phase 1 and 2 settings and SA lifetimes but still once a day the connection is terminated. The other tunnels on the Watchguard never disconnect like this. Has anyone come across this problem? Or has any ideas?

I see this 'feature' on our drayteks (2600/2600+/2800/2820/2900) to watchguard x1000 vpn connections.
doesnt really solve it but you could make your draytek vpn profile always on, this would make it a 'dial out' connection.
It seems that the draytek will always reconnect after 24 hours albeit with a small downtime while it renegotiates.
Where as on a two way vpn the watcguard would not always renegotiate/reconnect (if the watchguard was the initiator) after 24hours - even if there is traffic