Is 2012 I bought the Premier Passport pass. This pass is good in both WDW and DL for one calender year. It cost around $800 at the time. I was living in Las Vegas NV at the time so going to Disneyland was easy. When I found a cheap flight on Southwest I would go for the day. I would do that 6 times I would do day trips there and when I went to WDW I did a 10 days stay.
It was worth the cost vs buying tickets for the days that I was there. Now the downside. It too a lot of energy. I don't live in Las Vegas anymore.
Now I live in Arizona. So day trips are not easy anymore so I bought a Annual Pass at Walt Disney World.
The pass cost me $700. Now I'm doing two trips to WDW The cost for ticket for 7 days would cost $400 so two trips would be worth the cost of the pass.
So if you are planning at least 2 trips in a calendar year it is worth looking into the Annual Pass.