3 1/2 hrs is good!
i didnt like the thought of all that urine next to my babys skin at all, so changed to pockets recently (after months of trying them all out and finally deciding today!) It would be good idea to fold the booster if your little man pees more upfront. But that depends on how much time he spends on his back/front/sitting up.
Also, you might want to try wool covers (longies, soakers etc), as it lets the pee evaporate and keeps the nappy a little less wet. You dont get the smell either. Theres always wool on classifieds going cheap for newborn sizes. x