Girlie the answer to that question is, it depends. For Panto the girls get 2 free tickets each. Depending on sales, we can often get cast price tickets.
But for bigger touring shows, we may be able to get reduced tickets at the last minute, or later in the run if there are lots of tickets left.
Last time DS was in the West End, we weren't offered any reductions at all. Generally, if I want to go on a specific day (e.g. My birthday) then I suck it up and pay full price. Same for taking the two grannies, there is any one Saturday that I am not chaperoning, so able to drive them to the theatre.
Other times, for example when I'd already seen Jesus Christ Superstar with DS and DD1, I didn't mind not seeing it again 3 weeks later, but I got a £10 ticket so watched it again.