I don't know how it is for everyone else, but I hate starting a toyline that ends without getting the core characters by the time it's canned. (Mainly SH Figuarts stuff, to use an example)
At the same time, I'm aware that burning through core characters TOO fast can kill lines as well. But going "balls deep" into EVERY LINE is an impossibility, due to budget, space, and time. For example, Storm Collectibles were more affordable back when they were on the 50-60 range. Now the cheaper Storm Collectibles figures are on the 80-90 range. And to this date, they haven't completed the core roster of ANY of their lines.