I give my daughters jumping pony holidays. Over the year I'll give her mini breaks turned out if she's been busy or got a busy few months. She had one after the Easter holidays before half term summer. She'll probaly get another one after the summer holidays then planning a minimum of 2 weeks over Xmas/new year.
She goes out jumping a lot and regularly does away shows so think it's important to give her time to chill and stop her getting sour. Works for us anyway.
I always give mine time off, usually for 2 or 3 months over the winter. The weathers rubbish then anyway and I really think if they've competed the rest of the year they appreciate time off to just chill out in the field. Has always kept mine nice and fresh and willing to compete. If I ever had a horse who just hacked or something then I might not but I generally compete mine and with jumping it does take a lot of effort so feel they deserve it.
Mine are off most of winter unfor because i have no arena and my mare is awful hacking on the roads. I give time of to my 8yro because she's a special case that will have a meltdown if too much is done and ten becomes (Very) hot headed if not worked enough - You really have to play it by year on her.
Generally only my uncle's hunters, I get to have a bash round the hunter trials on them and then they are off all summer. They get brought back in time for cubbing and the sponsored rides.
Whatever horse I have generally gets less work during the winter because a)no arena b)field is a mess and c)school! They are keep in work but it just goes from 5-6days a week to 2-3.
Mine get a few months off in winter, usually from when the weather gets really bad in December until it improves I'm March. I think they benefit from a break and come back better and I hate riding in wind and rain!