Let's say I send people in a static list and I want them in there for 6 months. Sharp. No matter what. Two options I see are:
A) I use a wait step of 6 months at some point. Something like: Was added to list // Wait 6 months + Remove from list. I've red in community and I still wonder if Marketo manages this well.
B) Create custom date field that is updated upon lead added to list and use that to remove the said human from list.
Option B would be my favorite one but I have 40 of those lists and I want to make an informed decision before create 40 custom date fields.