I know at least one person who does this ... I can't say i agree with it but it's his choice (and his pain if he gets caught either doing this or not having a valid ticket ... especially since they have started penalty fares around here).
Some of my other friends are lucky as they get free rail travel due to their work contracts but I just have an annual season ticket so I don't have to worry about getting a ticket for my commute.
It's impossible to be caught though.
The ticket, providing it hasnt been written on or stamped is valid for a month.
If it hasn't been checked, it's still possible to use it (unless you're an angel).
). If a guy comes along to check my ticket i'll buy one, if they dont then it's their loss.
... twas good that i did, since me and my mates ended up going to the station after the one i was expecting us to go to, and they had ticket-reading barriers, managed to pay for the extra bit of the journey, but had i have had my ticket from earlier on in that day, and he read the time (for some reason 
