Never say never
The following situations are generalized frequencies that are sometimes impacted moreso by the strength of my partner than the situation at hand:
I will (almost) always chase with no runners on and a trap/catch situation or near the line. (In fact, I did it three times in one game yesterday)
I will often chase with a single runner on and a trap/catch situation and be prepared to pick up the trail runner should their be a play on the lead runner.
I will sometimes chase with two runners on but only if I judge an absolute trap/catch situation and the its relative impact on the game (ie how close is the score and what inning). I am again prepared to pick up a trail runner should their be a play on the lead runner.
I will rarely chase when the bases are loaded unless this catch could end the game or inning in a hotly consted match. I am again prepared pick up a trail runner should their be a play on the lead runner.
All of this, of course, is discussed in the pregame by summarizing that the greater the number of runners, the less likely I am to chase, but if I do, I will be prepared to pick up trail runners should their be a play on the lead runner.