Constant lightning::ln::channelmanager::MIN_CLTV_EXPIRY_DELTA

pub const MIN_CLTV_EXPIRY_DELTA: u16 = _; // 42u16

The minimum number of blocks between an inbound HTLC’s CLTV and the corresponding outbound HTLC’s CLTV. The current default represents roughly seven hours of blocks at six blocks/hour.

This can be increased (but not decreased) through ChannelConfig::cltv_expiry_delta