If you are concerned about real problems or a break down on a long trip, here are a few things to zero in on with this bike, b4 your departure:
1) I read earlier that, most of the time a biker has issues on the road, regardless of the make, it's due to a dead battery. Make sure your bike's battery is topped off (if wet cell), test its ability to hold a charge, and ensure it isn't too old. Make sure all battery terminals/connections are extra clean, and tight.
2) Most stories I've read of the VN750 putting someone on foot during a long trip involve the failure of the final drive splines. Before your departure on a trip of real length, make sure
these final drive splines are properly lubed! A number of threads exist on this forum for details and specific info on this procedure.
3) Inspect your tires for proper air pressure, wear patterns and enough tread depth for at least the length of the trip. Consider installing "Ride On" tire sealant as a great hedge from having to repair a tire away from home--or civilization.
4) There are areas west of the Mississippi where the Vulcan's gas tank capacity will not get you to the next gas station. Be sure if you are touring out west that your intended trek has fuel available within your bike's fuel range--and when you'll be arriving at each fuel stop (hopefully, they won't unexpectedly close on you b4 you get there). Your other option is of course to carry extra fuel with you in these areas.
5) There are other threads on this forum that explain how to test the health of your bike's electrical system. This test is probably not a bad idea b4 a long trip, and also consider installing a voltmeter to monitor your bike's electrical system as you ride. Again, other threads exist here on the details for a voltmeter, too.
6) Use the search function above to look up the "phantom gas syndrome" and what to do to prevent it, and/or get rid of the problem before it happens.
7) As far as reliability issues specific to the bike, the above should keep you out of serious trouble most of the time...from what I have learned about this bike (assuming that you've done satisfactory preventive maintenance on the bike, otherwise). Past all that, you're most likely to have issues with seat comfort, if you are still riding on the factory, unmodified seat. I would suggest a trip of shorter length (less than 250 miles) in one day, to see if the seat comfort is satisfactory, or not (if of course you haven't already resolved this problem to your satisfaction). Several options exist to correct or minimize this, including adding new footpegs (via crashbar) or floorboards....but nonetheless the factory seat is easily the worst of this bike.
Keep us posted on your upcoming journey with a description, and pics....as those kind of threads are easily the most interesting....