It depends on the character. Some of them don't come back.
It's kind of an inevitable problem though. Since this is a cultivation novel, the mains are always advancing, and naturally they advance a lot faster than the side cast, so they tend to get left behind in terms of power by design (or they're on a tier of power way above the MCs, which is its own reason). It also doesn't really make sense for a lot of the side cast to follow them around. They show up when it makes sense for them to be there.
Like it's not like it's unnatural. The side characters disappear either when the main characters outstrip their power and they're left behind in whatever location they were last at, or if they're too strong, when the characters can't have a supremely powerful crutch to lean on for the coming story. Honestly I hesitate to really call it a flaw.of the series, it's just something I've noticed and went "it's kind of sad that I haven't seen X or Y for four books"