There are a lot of good advices here. I wouldn't want to comment on how long you can safety travel in a day b/c everybody is different. But one tip I would like to pass on: NEVER arrive at a campsite after dark.
I have done some 600 mile day which took me 14 hours including an unscheduled stop at a Costco to replace a dead TT battery. For those type of travel, we would have meal breaks at rest areas. Dog & passenger exercises while pre-cook meals are getting readied. At the end of the day, I'd pull in a Walmart parking lot and hit the sack for 6-8 hours then move on. No unhooking would be involved. We would make a point to replenish supplies in the morning before we leave. And the next day's travel time will be cut in half arriving destination at mid-day. I rarely do 2 long days in a row.
Since you are new to this, like everyone here has said, do a few short shake-down runs nearby before the long trip to get used to your TT is advisable.