No developer will ever be able to produce enough ready-to-play themepark content fast enough to stay ahead of the players' capacity to consume it. And yet themepark MMOs seem to be all the industry wants to pursue.
So what can be done?
First of all, decide how long you want an installment of your themepark content to last. In other words, how often do you feel you can produce an installment of new content. If you can do an installment each month, then assume 30 days.
How many quests will be in your content installment? Let's say 10. Now by quests, I should clarify by calling them stages in a quest chain. Essentially what the current content installment is about. What you do is set a time lock on each stage on the server side which will pad out the content for the full 30 days.
Day 1 - Stage 1
Day 4 - Stage 2
Day 7 - Stage 3
Day 10 - Stage 4
Day 13 - Stage 5
Day 16 - Stage 6
Day 19 - Stage 7
Day 22 - Stage 8
Day 25 - Stage 9
Day 28 - Stage 10
Some may say, "I don't want to be gated from content. I want to play through it all at once!"
For what I suggest to be fair, If I come into a quest series 20-days after it is released, then I would have access to stages 1-7 which I can blast through in one day if I want to. But when I complete stage 7, I won't be able to play stage 8 until day 22.
I would rather wait three days between stages in a content installment than wait almost a whole month. Time-delayed release of content makes the content last over the course of a predetermined period and reduces wait time between the new things to do.