The best would be romance between PCs. If that is not possible, make another player play the romantic interest NPC. Otherwise it's just waiting time for everyone else.
The best would be romance between PCs. If that is not possible, make another player play the romantic interest NPC. Otherwise it's just waiting time for everyone else.
Shouldn't everyone else be the judge of that? That sounds more like a situation where the players in an individual group are bored with too much interaction between a PC and an NPC, either because of disinterest in following the developing situation, or because the DM isn't making it enjoyable for them, rather than a generalized rule about what doesn't work.
Of course, you do have to know your players and their interests.