With our first daughter we used the Snugride until she was 14 months old. She was small and we would have used it longer, but loaned it to a friend. We then moved her to the Britax Marathon. We had a base in each car for the Snugride, and then invested in two Marathons - one for each car.
I had twins 6 weeks ago and we're again using the Snugrides (had to borrow one from a friend). Mine were a little over 5 weeks early, so not even 5 pounds when they came home. I could not imagine getting them in and out of a car seat at each errand or appointment. The Snugrides are wonderful!
With my older daughter, we got the Graco Travel System. That stroller was so large and bulky that we didn't use it much. Instead, we got a Snap N' Go and loved it. I bought a double Snap N' Go at Once Upon a Child...worth looking into, as they are $100 new at BRU. I wouldn't do it any other way...the Snugride and Snap N' Go are life savers.
When the twins are big enough (at 6 weeks, neither one is on the growth charts yet), we'll move them to the Marathons. I don't know that we'll get two for each car this time around and will have to see what our childcare situation is at that point.
Congratulations...and I hope you have help lined up. We don't have any...my husband doesn't think we need it. Since he's not doing the lion's share of 'chores,' he's fine with it. No LOL here...