I manage accounts for 4 family members. 6 airlines means 24 accounts, of which 9 are currently under 10,000.

I save the miles. The challenge is to keep them from expiring. But assuming that we are successful at that (there are other threads about this), I think there is a lot to be said for the infrequent frequent flyer. We have eventually gotten tickets that we never expected, because
1.) You never know when airlines will merge
2.) You never know when a sale or schedule might put you on another airline
3.) You never know when you'll fly some airline overseas that has a partnership with an airline you usually don't fly.
4.) You never know when some promotion comes along so you can get easy points