Aux fuel tank yes or no.

I had a BMW GSA and could comfortably do 300 miles between refills and was glad to get off the bike,
I take shawn K's point about value I currently run Yamaha T7 that will do 220 miles per tank although 200 is a more practical range with a 2 ltr can as a back up.
Camel ADV have a 5 ltr aux tank £ 369 from Rugged roads a nice piece of engineering and will give 75 miles you would not want any more extra capacity is it worth it??