It was 3 days... (or more correctly 72 hours)...
and then it was changed to 336 hours (14 days):
/** Default for -mempoolexpiry, expiration time for mempool transactions in hours */
static const unsigned int DEFAULT_MEMPOOL_EXPIRY = 336;
In any case, individual nodes can set this value to whatever they like... so while the default is 14 days, it can theoretically be any number of hours...
I assume the 1sat/byte fee is from people using legacy addresses and not the segwit/native segwit addresses (mostly).
The fee rate used doesn't really have anything to do with address type used... Regardless of Legacy or SegWit, if you (or your wallet) selects 1 sat/byte as your fee (or 0.00001 BTC/kB), then your fee rate will be 1 sat/byte. The total fee amount paid will go up or down depending on total transaction size... but the actual rate per byte will not.