How long is a staking epoch?

Staking epoch is 1 week approx.

Not quite my friend. First, you need to check the explorer. See pic below.

1 week is for 3 seconds Average block time. We are at 8 seconds Average block time now, so 18 days, 16 hours.

The Average block time when from 3 seconds on epoch 13, 5 seconds on epoch 14 and now at 8 seconds on epoch 15

8 sec block = 18 days, 16 hours
7 sec block = 16 days, 8 hours
6 sec block = 14 days (14400 blocks per day)
5 sec block = 11 days, 16 hours (17280 blocks per day)
4 sec block = 9 days, 8 hours (21600 blocks per day)
3 sec block = 7 days (28800 blocks per day)