I do the same but I don't jump in right away. We have runbooks and escalation routines. If it gets to the point that I need to "jump in" I take that time back in the upcoming days and weeks.

As a personal favour I will fire off a private message to whichever colleague is on call if I see they are floundering. Because I'm a good guy and believe the help I give today may be requited down the line.