Ok, so I have thrown 900 Global since their first release. The Break. Compared to the Black Widow back in the day. 10 years later, that core is still in the line, and it just works. They more than made their money from it, and now allow it to be sold for less, but you will not find a 900 Global fan that doesn't like the Break core. You drill an Ops and you KNOW what you're going to get.
Now, when it comes to higher end stuff, it starts getting more tricky. Ball companies feel the need to refresh their lines, but in reality, the tried and true balls only come out of the fray when others fail. I love the SRC core, which gives me a different reaction than the Break, but it's good for me. The Train core... not so much. Bounty core, not so much.
I respect Motiv for maintaining a set release schedule and having a purpose for each ball. They seem very thought out, and a lot of their balls have been in the line for more than a year. Shock, Remix, Paranoia, all been out for much more than a year. That says something for them. They get rid of one reaction for a condition, and replace it with something that is better.
The release schedule is a thing of a past for most companies. Now it's just like "Let's see how much crap we can throw at the wall and see what sticks."