We just have joined everything. If we split, it would be 50/50 but I'd probably end up giving her most of the stuff, I already find that we have way too much stuff as it is. I like the simplicity of it all even though it might not be advantageous financially for me.
Personally, I find that "fun money" is the easy part. We both splurge from time to time but it is reasonable for the most part. The hard part is the big shared expenses which you'll never be able to cover with "fun money" or it sucks to do alone (house renovations, cars, trips, entertainment etc.) for which 1 partner doesn't see the value of the shared expense.