swmtr

TLDR; You can keep channels open indefinitely. There are 6 special situations when you want to close a channel listed below:
1. You want sats on-chain
2. Your peer is offline for too long
3. Hardware is struggling with too many channels
4. You're moving to a new node
5. You'are going offline for a long time
6. You're profit oriented and the channel is not profitable or very profitable

BTC_LN

Adding to "#2 peer being offline for too long", you might want to close the channel if the peer too long time to respond (high ping).

This can be very bad for people actually wanting to do payments on the network, as no one wants to wait tens of seconds to do payments.

Furthermore, if the channel peer's internet connection is unstable eventually goes offline while there is an inflight HLTC, it can lead to nasty force closures.