I wouldn't like to try that - whilst you don't have to be going immediately to the games, the tickets are designed only for those going to the games.
In theory if you had a ticket for the opening ceremony of the Olympic games and the closing ceremony of the Paralympic games then I think you'd be fine to travel whenever you wanted.
The terms
http://www.nationalrailgamestravel.co.uk/terms-and-conditions/2012-games-day-train-ticket/
don't say that you must be travelling to the Games.
There is also no restriction on outbound dates - the Paralympics end on 9th September, so it would be logical to restrict outbound travel to the 9th of September or earlier, but they don't - you can still buy tickets to London Games etc. up to the 9th.
If I were challenged I would point out my full compliance with the published terms.
I read that as meaning that if you bought a ticket to return on the 5th September it would be valid up until midday on the 6th instead of the usual cutoff of 0430, not that the return ticket could not be several days after the event you'd booked for.
Indeed, this is presumably to cater for late-running events and last trains that don't match up with them.
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This is incorrect.
The National Rail Games Travel website states that:
As an added benefit, your return journey is valid up to midday on the day after your booked date, in case you want to hang on and enjoy the atmosphere after your event has finished.
Therefore, you cannot use Games tickets to commute in days following your event.
No.
http://www.nationalrailgamestravel.co.uk/terms-and-conditions/2012-games-day-train-ticket/
"Tickets for the outward journey, i.e. to London or one of the co-Host cities, are valid for travel at any time on the date shown on the ticket.
Tickets for the return journey, i.e. from London or one of the co-Host cities, are valid for travel at any time on the date shown on your ticket and up to midday the following day."
Quite clear - this is additional flexibility for the walk-up single fares, to allow you to use it the following night, they are quasi-returns, even though sold as a single.
The Advances have a similar relaxation of terms:
"Tickets for the outward journey, i.e. to London or one of the co-Host Cities, are valid ONLY on the date and train service(s) shown on the ticket(s).
Tickets for the return journey, i.e. from London or one of the co-Host Cities, are valid on the date and train service(s) shown on the ticket(s). If you are delayed, your ticket can be used to travel on services up to three hours after the booked service shown on your ticket, or the next available service where this is more than three hours after the departure of the specified service. However you will not be able to use your reservation on any alternative service."
http://www.nationalrailgamestravel.co.uk/terms-and-conditions/2012-games-advance-train-ticket/