Moving your child through the various stages of car seats can be expensive, especially with the average price of a new convertible seat right around $175. 

The key question for parents, of course, is when to upgrade. There are various factors to consider, but parents should be careful about making the switch too soon. The child's safety should always be the primary goal.

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In order to cut the cost of a new seat, there are trade-in events like the one being offered by Target, which runs through Sept. 22, 2018. Target offers a 20 percent discount on a car seat or stroller if shoppers turn in their old seat for recycling. Bring an old seat to Target's Guest Services desk and the store will give you a coupon, which is good in-store or online through Oct. 6, 2018. Parents who don't live close to a Target store should check with their local baby-product retailers to see whether they'll let you trade in your car seat.

Consumer Reports' car-seat buying advice and ratings can help parents through the process. Our child-seat testing team offers these tips below to help parents decide when is the best time to upgrade.

Thinking about picking up a used seat cheap? CR's child-seat experts don't recommend it. Buyers usually can't be 100 percent sure of a secondhand car seat's history, including whether it has been involved in a crash, its expiration date, or its recall status. Without that information, children using such a seat could be at risk.

When Should You Upgrade Your Child's Car Seat?

When your child is too big for an infant seat. Many rear-facing infant seats have weight limits of 30 pounds or more, but most don’t have matching height limits. So don’t be surprised if your child outgrows the infant seat long before he or she reaches the weight limit. 

Your safest bet is to trade up to a convertible seat, which can face either the front or back of the car, and continue to have your child face the rear.

When your child hits 1 year old. Based on our most recent recommendations and tests results, if your child has reached his or her first birthday and still fits in a rear-facing infant seat, the safest move is to switch to a rear-facing convertible. 

Our newest test methodology includes simulating what happens in the event of a crash. In those tests, we found that a 1-year-old child was far more likely to hit his head on the back of the front seat while in a rear-facing infant seat than he would be if he were riding in a rear-facing convertible seat.

When your child's car seat has expired. Many parents don’t realize that child car seats carry expiration dates. This is particularly important when you have several children and use the same car seat for each one. 

The owner's manual or seat label should tell you when the seat was built and when it should no longer be used. The life span is usually six years.

Expiration dates ensure that key components of the seat haven’t become too worn and that the seat meets contemporary safety standards, which are always being raised. 

If your child's seat has been in a crash. Most seats can be reused after a minor fender bender. But the National Highway Traffic Safety Administration (NHTSA) recommends replacing a seat if it was in a collision that either involved injuries or required the vehicle to be towed; if the airbags were deployed; or if the seat, or the door nearest the seat, was damaged.

If the seat you've been using has been in such a crash and you haven’t yet replaced it, a trade-in event could be a good time to do so.

When your child's car seat is damaged. Daily use, heating and cooling cycles, and less-than-careful storage can take a toll on a car seat’s structure. Parents should check for cracks, loose parts, and worn straps and fasteners. If the seat is damaged, it may not offer as much protection in a crash as it needs to.

Even if you’re trading in for the same type of seat, one with new, undamaged components will provide better protection.

When it’s simply time for the next step. If your child has outgrown his or her current car-seat stage or is close to doing so, a trade-in event may be the best time to make the move.

Don’t rush the process, even if the savings are tempting. Other than moving from a rear-facing infant seat to a rear-facing convertible seat, other transitions may be less safe for a child. For example, a forward-facing seat is less safe than a rear-facing seat, and a booster is less safe than a forward-facing harnessed seat.

If you're unsure about what to do with a retired car seat, use CR's interactive decision tree in "Can I Reuse or Donate My Car Seat?"

Use the timeline below to find the right car seat for your child.

Consumer Reports Car-Seat Timeline shows when to Upgrade Child's Car Seat