You can drive it forever like that. But more importantly why is the front driveshaft vibrating? Your lift isn't tall enough to cause the front driveshaft to vibrate just for that reason. I'd find what's causing the vibration than continue just disconnecting it. Could have just lost a balancing weight or it might have a bad u-joint, I'd take it to a driveshaft repair shop and have them figure it out.I hope it's okay.
I have disconnected my front driveshaft (to reduce vibes) on several cross-country trips.