Once you succeed in getting a green card, it becomes one more card in your wallet, like your driving license, that you need to occasionally pull out and show someone. It is easy to forget how much effort it took you to get it.
Replacing it will be a hassle or might not even be possible, so you need to do all you can to protect it. Despite that, there will undoubtedly be circumstances when you need to renew your green card:
If the name on your card is no longer correct
Whether you have officially changed from Marvin to Sharon or from Ms. Rogers to Mrs. Brown, you need to update your card to reflect your new legal name.
If you no longer have your old card
You need to carry this card on you all the time, so whether someone stole it or it fell out of your wallet, you need to get a replacement.
If the data on the card is illegible
While these cards are plastic, you can still inadvertently damage them to the point where you cannot read them. For example, if they melt in a fire or acid spills on them.
If the card is about to expire
Most green cards are valid for 10 years, although conditional ones only last for two years. Like any immigration issue, the transaction can take much longer than you think, so do not leave renewal to the last minute.
There is a lot to understand and keep track of when in the country without full citizenship. Getting legal help to deal with all immigration issues is your best route to ensure you can stay here without problems.