A residence card usually lasts up to 5 years. You do not need to apply for a residence card to prove you can live in the UK unless you're both:
You can currently apply for a permanent residence card if you've lived in the UK for 5 years.
However, you do not need a permanent residence card to confirm your residence status in the UK unless:
you're an extended family member of someone from the European Economic Area or Switzerland and are yourself not an EEA or Swiss national
you want to apply for British citizenship
you want to sponsor your partner's visa application under the Immigration Rules.
Your residence card will not be valid after 31 December 2020. You and your family can apply to the EU Settlement Scheme if you want to continue living in the UK.
You're eligible if both of the following apply:
you've lived with your EEA family member in the UK for a continuous 5 year period
your EEA family member has been a 'qualified person' throughout the 5 years or has a permanent right of residence
You can also get permanent residence if you've lived in the UK for a continuous period of 5 years:
as the extended family member of an EEA national and you've held a valid EEA family permit and a residence card throughout
first as the family member of an EEA national and then with a retained right of residence
as the family member of a British citizen, if you entered the UK under the EU law after living in an EEA country
You can get permanent residence before 5 years if either:
you were living with your EEA national family member, who was working or self-employed in the UK, immediately before their death
your EEA national family member was working or self-employed in the UK but has 'ceased activity' (stopped work or self-employment because of retirement or permanent incapacity, or because they're now working or self-employed in an EEA state but are still resident and return to the UK at least once a week)