I'm still not clear in what way TOC staff think that writing-or stamping-a date on a ticket is any sort of proof that its being misused if the ticket is used several weeks later. Some of the comments on this thread seem to assume that any break of journey would only be for a few hours or overnight at best.
Condition 16 states: 'You may start, or break and resume, a journey (in either direction in the case of a return ticket) at any intermediate station, as long as the ticket you hold is valid for the trains you want to use.'
There's nothing there about it being a short period. As I read it, if you have a ticket valid for one month, you travel outward on day 1, also start your return journey on day 1 but break the return journey on that day and then do all the other things in life (including multiple other journeys with other tickets) for the next 29 days, you can still come back to your break point and pick up use of that ticket to finish your journey on day 30.
The concern I have about some of the comments is the same as that of Barry Doe-that writing or stamping a date implies that there is something illegitimate about using the ticket after that date.