You can change the oil in 10-15 minutes, even less if you forgo the oil filter and change it every other OCI. I don't recommend that, but some do it. Oil filters are $7/ea, oil filter o-ring is $3/ea, drain plug o-ring is $2/ea. Honda GN4 10W-30 is $6/qt, buy six quarts and you can do the first five OCI's. Some replace the o-rings every other OCI, but I replace mine every OCI, an extra $5 every 1,000-ish miles isn't going to break me lol. So at retail prices you can do a complete OCI with new oil, filter and o-rings in under 15 minutes for less than $20.
I drain my oil into one of those round plastic oil pans and then add it to my 15qt oil container which I take to the city recycle center to dump when it gets full. You can possibly increase the oil capacity with a Hinson or Rekluse clutch cover but I have yet to confirm whether or not they do and if so by how much. I will be replacing mine if I can get confirmation of an increase, no replies from Hinson or Rekluse just yet.
The 450L has very good on-road characteristics for it's class, just looking at it you wouldn't expect it to perform almost as well as the 250L on the slab but it does. You talk of these 1,000 mile trips and I think you'd be fine on the 450L for that type of riding, just throw some dirt and gravel in for the Elle along the way to keep her happy. The first thing I would change on the bike, especially if you're going to put down that kind of mileage would be the seat, the factory seat is horrid. Acerbis and Seat Concepts both have seats for it and I'd look into Enduro Engineering as well, but I am not sure if they offer one for it yet.
In regards to the video, he makes some good points, too many key board warriors bickering over tiny silly details instead of getting out and riding. I don't think that ADVRider has gone down the crapper but it has certainly changed over the years, but what forum hasn't? In regards to the fuel tank, I don't see the need for anything bigger than the IMS3.0, if I need more I bring a bladder or MSR bottles. The 3 gallon doesn't take away from the looks, feel or handling of the bike, you get into those bigger tanks and they are not only ugly but they change the cockpit space too much and will certainly start to impact the balance and handling.