I agree with Hugh--the more generations, the more useful. Yes, It takes a long time to load the 15 gens, but worth it because revealing.
To Magnus and others: the only tree* I could download to a gedcom file is full of errors. I'm trying to be very careful about what I add here on this site, but when I see the 15-gen Family List, I see names that have had to come from someone in Wikitree deciding their tree and mine should be merged, so I have many people I've never heard of and can't stand up for in my now 15 gen Family List. Should I consider these valid names for my tree if they haven't shown up on my error list?
*Well, not exactly accurate: I have three trees for one family on my ancestry.com list. The largest one is the problematic one**. If I gedcommed it, I wouldn't want to have anyone here at Wikitree involved in cleaning it because that is like cleaning the dump except for the 2000 1/2-gallon milk cartons which must be piled neatly according to condition found. Simply unfair, don't you agree?
** I do have a somewhat smaller, more cautious and mindful one but it's very incomplete. My thought is to proceed with it as my "working tree," taking suggestions to analyze prudently from the larger one before adding to my more cautious tree. Does that sound practical to you? It seems to leave me asking questions perhaps too regularly.