Have any of you used a Britax for rear facing up until 2?

Britax are actually among the shortest car seats that will allow for the least amount of time rear facing. They also have very little leg room, which is not a safety issue but can lead to uncomfortable children. Leg room is not a comfort issue in almost every other seat. They should get most children (barring tall and/or long-torsoed) until age 2, but that's really a minimum and your aim should be closer to age 4 http://www.nhtsa.gov/ChildSafety/step2. Proof that older kids are happy rear facing past 2 http://www.photoshop.com/users/CarSeatsAreCool/alb...

The current Britax convertibles expire 7 years after Date of Manufacture.

My list of recommended seats, rear facing weight limit in parenthesis

Sunshine Kids Radian (now Diono) (65SL (now R100) - 40 lbs., 80SL (now R120) or XTSL (now RXT) - 45 lbs.)

Britax Marathon 70/Boulevard 70/Advocate 70 CS (40 lbs.)

Safety 1st Complete Air (40 lbs.)

Learning Curve True Fit models (35 lbs. but taller than most)

Maxi Cosi Pria (40 lbs)

Graco Size4Me70 (40 lbs)

Graco MyRide 65 (40 lbs)

Evenflo Triumph 65 (40 lbs.)

Evenflo Momentum 65 (40 lbs.)

Cosco Scenera (35 or 40 lbs)- this would be a good budget/travel seat, but won't accommodate most children past age 2 or 3

For expiration dates and measurements, http://www.car-seat.org/forumdisplay.php?f=66 you'll want a shell height (not including headrest) of a minimum of 24 inches.

Always meet with a CPST after reading your car and car seat manual to be sure you're installing and using your new seat properly http://www.seatcheck.org/

*ok, another edit :)

Your Britax won't fit your newborn. The new versions have infant inserts available, but yours doesn't. The bottom harness slots are around 10" on average, so most babies won't fit properly in a "Classic" Britax until at least 6 months old, some not until a year. When rear facing, the harness must come from at or below the baby's shoulders, and the average newborn's torso is much closer to 7" than the 10 required for your seat.

Your seat expires 6 years from DOM, not 7 like the new ones.

I would keep the 4 year old in the Nautilus, the 3 year old in your Britax and either use a cheap infant carrier (Cosco Comfy Carry Elite) from birth for the newborn, or a cheaper convertible seat like the Scenera. Once baby fits in your Britax you can move him/her to that and you'll either have a spare convertible, or you'll have only spent a little money on a carrier.

If you're trying to fit 3 car seats across one row, my recommendations will change.

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Passing the car seat test doesn't mean they fit. Nurses are not CPST's and are not qualified in any way to tell you that your seat is being used correctly, they can only tell you if your baby maintains proper oxygen levels in the seat. Unless your Preemie had an extremely unpropotionately long torsion, (s)he didn't fit correctly. Visit car-seat.org and search boulevard newborn and see the answers.

Yes. My son rode rear facing in a Britax Roundabout until past age 3, when he got past the height requirement (his head was higher than top of shell). My son is extremely short and slight.

My daughter is 20 months and still riding comfortably in the same seat rear facing. She is average weight and slightly taller than average in height. I don't think she'll make it to age 3 rear facing but unless she hits a huge spurt we should make it to age 2.

The seat I have is about 4 years old, I got it when I took my son out of the "bucket."

Yep! Leah was RF in a marathon until a couple weeks ago but the seat expired.