as an 11 year old i was often the toast of the team because i went in and blocked out 3 overs. It made me feel like i was the star, i had not just turned up to make up the numbers and field 3rd man/fine leg.
if i had been playing this win or lose stuff i would have just gone in and done whatever, no one would have said anything to me and I wouldnt have got the buzz i got when they all clapped me off and gave me a massive wedgey in the changing rooms to celebrate. Once blocked out 20 overs with the other young lad at number 10 to save us from defeat, the other team was livid, we were on a massive high. By 14 years old i was opening and scoring hundreds. Doubt i would have been able to do that step up to opening if i had been playing win or lose cricket, i managed to work on my temperament, concentration and not get phased at all. By 16 i was playing ECB league (wasnt called that then) and batting 7 and standing up 50 overs every game ..... sure thats why i fell out of love with wicket keeping
I think timed games are good for kids, no pressure at all. If there is a big total, play your own game and if its get close with 15 overs left then you can try to win.