We just got back from our first trip to
Disneyland. We were there 8 days, but in the park 7 full days plus only 1 hour on our first day. I wanted to see everything, but knew that would be impractical with two young children in tow.
As it was, we hit most of our 'must do' rides (in both parks), met many characters (I haven't counted them all up yet), saw the Parade of Dreams, the Block Party Bash and the fireworks and attended two character meals.
We
did not find hidden Mickeys, or all the pressed penny machines (we pressed pennies for our favorite attractions, though.) We did not see shows except for Playhouse Disney, did not tour the tortilla factory or Boudin's Bakery, did not bake cookies, did not visit the 50th historical presentation or view the Disney animated shorts at the theater on Main St. We did not sail on the Columbia, meet villains at the Villains' Lair or hit too many rides at DCA.
We went (last week) at a time of year when it's not terribly busy, so I can only imagine what it would be like at high season!
I think it's true that you just can't do it all in one visit. Even with our 8 days and all the fun we crammed into each day, we were ready to go home by the end and were flat-out exhausted!
However much time you have to spend there will be great and action-packed! My philosophy is this:
Go into it concentrating on what you most want to see and do and try to get all that in. If you have time to fit in some other fun, then great. Whatever is missed you can hit on your
next trip!
It only took us 13 years to make our first trip to Disneyland, and we're already planning to head back within the next year or two!
). 
but 
Any amount of time at all is great, because all Disney time is great time.
