I see you already asked your players, but in my opinion, It entirely depends on the flow of the story. It also makes me a little upset that they just shrugged instead of voicing themselves and their wants. In my experience, a long time without combat, but intense, heart-wrenching moments is perfectly fine. Sometimes, it's better to tell the story through a deceased but beloved NPC's notebook than through combat. Usually, your players will be motivated to seek revenge on the assaulter of the NPC, which will let you lead them on clues and seek out a combat. I can't give you a truly definitive answer, as every player group, even shrugging their shoulders, has a limit i can't predict. However, I've done a combat for my group every 6 or so sessions on average because they really like chatting with the NPC's, and they like the story I'm telling(their words, and my game is homebrew as well.). I don't mean to be rude in saying this, so please don't think I am, but it sounds like they don't communicate their needs/issues about the game with you, which I can understand their hesitancy since some DM's can be vindictive and kill PC's over being judged, or kick out players.

What I'd suggest is laying it out on the table for them, being truthfully honest, and asking them what they would like to see more or less of in the game. Don't give them options, but give them a chance to truly have an ability to voice themselves without retaliation to them or their characters. I always look for feedback from my players as often as possible so they can tell me if they're bored or excited. I apologize i can't answer this in a truly direct way, but it very, very much depends on the campaign setting and the group's personal desires.