I've been watching a British soap, Hollyoaks, on Hulu. I've seen 60 episodes and I still haven't seen all the characters. The pacing, sets, everything is top-notch, but a lot of characters seem to float for months with short one-off appearances. It really works for streaming though.
I have been wondering if this model could be applied to US soaps, especially Days and the upcoming The Gates, as having a front-burner storyline for every character just isn't possible. A lot of the "older" characters on Hollyoaks own businesses (like the bar, the restaurant, the grocery store) and they relay their experiences to the younger set (based on what was shown on screen in the 1990s/2000s). It really works and is a stark contrast to Days with its constant repetitions and flashbacks.
Kayla can spend 70% of her time as a doctor, Steve as an investigator, Marlena as a doctor/psychiatrist, etc. Parenting their kids/grandkids can be 20-25%, and having cute scenes every now-and-then to round out their time. Keep them in Salem, together, and active - but focus the drama and upheavals on characters with <35 years on the show.
But to Poirot's point, they should be seen and it should be easy to remember when we saw them last! Characters do seem to vanish for long periods without explanation.