When I go into an elevator, the WIFI / 4G connection can drop for half minute for example, then it reconnects later.
Or for example switching from one wifi network where the connection is slow to another one (my fast tethered mobile network).
Remember, your identity in a TCP connection is your IP address. If you connect from another IP and want your session to continue, identity must be handled higher in the stack.
TCP connection technically live forever by default. It’s up to either party to complete the handshake. Without that mechanism, your box would run out of ports.
The essential tuple of a stateful IP session, the "5-tuple," is the source IP address, source port number, destination IP address, destination port number and the IP protocol number, in this case TCP. None of those elements can change during the lifetime of the connection. Or rather, changing any element constitutes a different connection.
Not that you needed to be told that; you probably know this already. It's just an interesting factoid that I imagine others might find interesting or useful when thinking about networking. In the guts of every device that handles TCP state (clients, servers, middle boxes, whatever) there is a table of all in-flight 5-tuples that marries every incoming packet with some state.