Last year was my first time at kiddy tbh and i ran 2 practices, 4 heats and a final on the one set of green ballistics. They were quite literally bald and with holes in by the end and the grip had just about gone by the final.
That was in 2wd, they were very worn on the front also like..
I reckon i'll get a set for the 2 and a set for the 4, no more, take it easy early on in practice to save them and then go for it in the first few rounds and see what happens for the final..
other way is to try scrounge some from a top driver who is runnin a set a run!
I dint feel any real lack of grip until my final.