...I can say that an older sohc will tolerate long journeys on a regular basis with absolutely no concerns about reliability. That is, of course, assuming that the 'care and feeding' aspect of the bike has been looked after.
These bikes are remarkably straight forward to maintain, even given the fact that there is four of everything. Armed with a factory service manual, some basic tools and a little zest for fettling I found that after only a couple of months of ownership I could do a full tune-up (oil/filter/check plugs and air filter/check and adjust valves/balance carbs) in about an hour and a half. As you know I am a devotee of the Scottoiler, which takes care of the chain.
As for the 'touring'... I used the bike to commute to and from a Monday to Friday job 440kms away every weekend with no issues. I also rode her up to and back from Fort St.John, a distance of 1000km, again with no issues of reliability. I use a tank bag all the time for wet weather gear, tyre repair stuff, first aid kit etc and just bungeed a bag on the back of the seat for the rest.
The bike cruises happily at 110-120kph which is a speed I am quite comfortable with. There is enough snap on hand to do a fast overtake, but frankly, being a GHOF with my speed demon days behind me, I don't feel the need to go faster.
I would have no second thoughts about jumping on the bike and crossing the country......if I had the time!
As for this year; she will be pressed into service for a several-times-a-week 110km each way commute to my latest job, as well as being the 'Event Co-ordinator' transportation for my Motogiro BC event happening at the end of June.