so......now you've got me thinking mel (sorry to hijack!) but what do you do with a maxi rider once your child hits 18kg? do you have to change something?
We were looking into this last week - you can buy a H harness for it. I think that it only goes up to 26kg if you change the seatbelt type over. Target sells the H harnesses specifically for maxi riders for about $50 (so I assume when they have 20% off baby stuff they would be $10 cheaper). They have a special clip that attaches at the top near the baby bolt. We have AHR Maxi-riders (I have one for DD1 and one for DS at the moment). I assume the H harness would be the same for AHR and normal maxi-riders.

Mel, we have issues with car seat - more getting 4 of them into our car (a 2006 Tarago) while still being able to get to all of them because my kids can't do up their own buckles or undo their own buckles yet and I am in no hurry to teach them. At the moment we have DS and DD1 in Maxi Rider AHR, DD2 is in a Safe and Sound Meridian AHR and our new baby will be going into our baby capsule for the first 8 months. We are thinking that we will probably buy another Maxi-Rider for DD2 when we need the Meridian for DS2. DH also has a car and will be taking DD1 to kindy and picking her up some days so we are looking into booster seats for her to go in DH's car so we don't have to keep moving them over. DD2 weighs about 14.5kg and won't be 4 until May so I have no idea what we are going to do with her because she can't really go into a booster seat just yet.

I reckon we will at least be able to use DD1's maxi rider for DS2 when he is bigger, but if she needs it until she is 7, then I don't know that I would want to pass it onto another child after 5 years of use anyway and I will buy DS2 his own maxi-rider in a couple of years.