My findings so far:
If it's a kit wine, it can be done and drinkable in a month. Best aged a year after that though.
If it's a JAO or other variant made with bread yeast, they're USUALLY clear and drinkable within 3 months, best after some age though, and doing anything other than the original recipe voids the 3 month warranty, some of my creations never quite cleared ;D
If it's a fruit wine or melomel, the fermentation should be done within two months unless you were mean to your yeasties, but it's anyone's guess how long it will take to clear, so budget 6 months if you use chemicals to stabilize and clarify it, longer if you want to go au naturel...
Traditionals should also be done within two months if you aerate well at the beginning and also use nutrients and energizer, but again, anyone's guess how long it'll take to clear.
Show meads (just honey, water and yeast)... well... I started mine a year ago and I don't think they're finished fermenting yet, they've been bubbling along slowly in their carboys but they're clear...
With the exception of kit wines (which I did two months before my wedding and all was fine), budgeting a year to a year and a half isn't silly if you want a particular wine ready on a particular date.