Subscriber lists and database usage


Hey there,

I got a client who has near 4 000 unique subscribers, but total subscribers is 26 000.

They have a lot of merged lists and seems everytime they make a campaign, it makes a new list from 10 sublists. Sometimes they want to send to all subscribers, sometimes just to 7 sublists. However everytime it makes a merged list.
So the questions:
  • Does the lists (26000 subsribers) give more pressure to my database?
  • How can they delete some of the merged lists? Right now they are saying it will also delete their campaign stats?
Best wishes,