Scam or safety? Do you buy $$$ it?

So, when it comes to buying things for the baby, the toddler, any child of any age, there are a ton of choices. There are more choices than than the ocean is vast...it's overwhelming. I can not and will not research everything. I will say that twice so I can hear it and possibly oblige with my more rational self...I can not and will not research everything. Thankfully or regretfully...I am no longer buying baby stuff. It was fun buying baby stuff...it's all so cute. However, I am past the money pit seduction of never ending cool stuff for babies. Now, we are into pre-school aged stuff and I notice that my car seat is going to expire soon. This car seat was previously used by my friends' kiddo and the 'due date' is now fast approaching. It was so nice to have been able to have access a used car seat. It's a huge blessing on a tight budget and it's recycling...bonus! I have tried to research car seats and expiration dates in the past and either the info was too confusing, non-existent or entirely based on fear tactics...but nonetheles, I never got a straight answer. Do plastics expire? Does styrofoam expire? Do they break down that quickly that they are rendered unsafe with in a few years? OR...is this a giant hustle? Maybe I am prone to conspiracy theories...lol...or I just have trust issues...who said that? Kidding...but this seems like a scam to me. Do I need to rush out and buy my kiddo a new car seat because it's expiring...or can we keep using it until he outgrows it? The fear factor is HUGE. Is it dangerous to use an expired seat? Is my child less safe? Are safety standards for car seats changing too rapidly and so you should change your seat out more often to have the best, latest and greatest in car seats? The Mom guilt seeps in...and tries to take over. If you have any real data, real answers...or anything really funny to add, please comment. Or if you have a car seat that is not expired, and you no longer use it and want to 'donate' it to our cause, eh-hem...please let me know. Until then...peace, love and sweet dreams!