Rynoth:
If the party has access to specific rituals then an adventure can be written assuming that they're available and can/will be used (warning the city that's weeks away, so you don't have to make the arduous overland trip while racing the clock, etc), or even that that specific ritual is the one thing that will save the day (good thing that the heroes are there and know it!),
Sure, but I don't think rituals should be specifically required or worked into an adventure, unless it's a McGuffin of some kind. Rituals should be like any other PC option: more or less likely to be useful, but not required.
Rynoth:
but pre-made ones don't have that advantage, so they tend not to address it unless the ritual is likely to be obtained in the adventure itself.
Sometimes NPCs in adventures offer restoration rituals. But I just think that the adventure writers could have shown more awareness of the existence of rituals and made some standard adventuring situations that would be at least a little easier with an applicable ritual. It wouldn't be hard for a situation to involve something that would be useful but is broken beyond repair, and for the adventure to list the cost of using Make Whole on it. And adventure could incorporate a treasure item that weighs hundreds of pounds, something like a statue or a throne or a sarcophagus lid; the players might find a way to get it out, or sell the location for money, or something, but for just 10 gp per day, they could simple take it back to town with them on a Floating Disk.
I believe that some of the skill challenges in Demonomicon even advise how to incorporate rituals in skill challenges. Too little, too late, though.
Rynoth:
So, when they do get used, you kind of have to wing it. Sometimes it might entirely bypass a major plot point or adventure segment, but that's okay - it's kind of the point of having that sort of trick in your arsenal, and rituals with that kind of potential are rarely super-cheap.
That's not okay with me, honestly, which is why I try to avoid having major plot points in my adventures.
I can wing it when rituals get used, but I'd also like there to be authentic reasons for players to say "I'm going to buy such-and-such ritual at the next opportunity, so this doesn't happen again."