Ben; to answer your questions in a DIY context;
1. If you've sent in an entry and don't let the organiser know you are not riding on the day the DIY cards is spent (whether paper or virtual) so it's always best to pre-check the route for distance and enter as you are about to roll out or the night before
Right, so let me just get this straight so I understand you correctly:
Am I right in thinking I am perfectly legitimate in doing the following:
* Buy one/a batch of DIY cards from DIY organiser
* Submit a route and say I am going to ride it on, say, 15th Jan
* On 14th jan, send an email to the organiser saying I am not going to ride it (so the card is "unspent")
* Wait till the weather looks nice, say it looks nice on 21st jan : so I send the organiser an email saying "I am now off out to do this DIY that I was going to do on 15th jan but didn't", and then 5 minutes later set off out and ride it
* return home with all receipts and send them in with the "unspent" card for validation
Sorry to be pedantic/hypothetical but it seems from what you are saying that it effectively allows me to NOT nominate my date in advance. Which I was under the (perhaps mistaken) impression that you had to do. This would suggest DIYs require one to be less audacious in terms of being at the mercy of future weather conditions, which thus frees up more audacity to enable you to be more audacious in terms of a longer/harder route at a more unseasonable time of year. (I'm not complaining - I think it's good if it is like that - I just want to clarify...and to check it isn't "technically allowed but a loophole that's frowned upon")