My view (definitely not 'the view'; others have different thoughts on this) from 15 years out:
For me, it doesn't make much of a difference. Does it for you? If so, I recommend figuring out what the differences are. They may be important to you; they may not be.
One way of conceptualizing Reconciling is 'building a new M.' This my main view. The process includes resolving issues, building bonds, (re)connecting with each other, etc. IMO, one aspect of virtually every A is that the WS is not honest about the issues that matter most to the WS, and R includes developing the courage to share one's priorities, concerns, discomforts - and comforts, joys, etc. Initially, the issues are primarily related to the betrayal.
As the A-related issues get resolved, day-to-day issues replace them, and they need to get resolved. The same skills developed in R are used to resolve the day-to-day issues. The process is the same. At the same time, people change over time, so a couple needs to continue to adjust connections to new circumstances.
IOW and IMO, then, R morphs into M. That's why I have no trouble with the proposition that R continues for the rest of a couple's life together. Even without betrayal, life is resolving issues, maintaining and adjusting connections, feeling, thinking....
At some point, some of us declare victory, but life before and after declaring victory isn't much different. It's like a birthday or anniversary - the day is just one day different from the day before and the day after.
Unlike b'days and anniversaries, though, each of us gets to choose when to declare we're reconciled. Each of us gets to and must decide for themselves when they're no longer in the R process.
[This message edited by SI Staff at 9:11 PM, Monday, August 3rd]