This, I think, is the right answer. Northern could just run the same Delay Repay scheme as everyone else. It seems to me that wanting to use the vouchers to their absolute, theoretical maximum is a minority pursuit limited to subscribers to this forum. So Northern could make their life much simpler and upset only the very small minority of their customers who contribute here by withdrawing the voucher scheme or tightening the rules.
It might be time for us all to stop grumbling that the good isn’t perfect.
I don't think your presumption is correct at all.
One of my former work colleagues rarely caught the train but one day he, his wife and his children were affected when two consecutive trains were cancelled on a line with an hourly service. He didn't want his children waiting for hours so got a taxi and tried to get Northern to refund it. Northern refused as there were still a later service that operated but issued the complimentary tickets. My former work colleague's response was to try and get maximum value from them given he needed for fork out for a taxi due to the delay.
You'll also find a lot of holders of the complimentary tickets are season ticket holders who much rather have a complimentary day trip to somewhere like Blackpool, Windermere or Scarborough then a small refund for the delayed train. Northern benefit from this as they get to keep 100% of the season ticket revenue and the holder of the complimentary ticket is making a journey they wouldn't otherwise have made, so Northern are missing out on revenue that way.
On the other hand this might be an example of quit while you are ahead. We do not want Northern suddenly introducing such conditions printed on the reverse of the next batch of vouchers.
Agreed. Although, I still have quite a few of the existing ones due to Northern's performance being poor for a very long time on the Mid-Cheshire line.