For example, my wife and I have 10-day non-expiring passes that we purchased in 2005, but the last two trips we have planned (October 2010 and October 2012), Disney has offered a free Dining Plan promotion for on-site hotel guests. The promotion requires us to buy a minimum 1-day park ticket, which we all know is a waste of money, so we have purchased enough days to cover our anticipated stay (without the non-expiring option) since the price per day ticket is lowest as you increase the number of days on the pass. So we have days stacking up that we'll eventually need to use, and we make sure to keep all of our unused Disney passes in a "safe" place.
Before the biometrics, you could just hand off or sell your passes to friends of family, but with the new technology, you've got to be the one to use the ticket.
To further back up my point, from http://disneyworld.disney.go.com/tickets-passes/noexpiration/ :
No Expiration* OptionWith this option, your unused Theme Park days and Water Park Fun & More visits never expire.
As for the no-expire tickets... I have a 10-day, no-expire ticket that I've been using for several years, never for more than one or two days per Orlando visit. I often choose instead to stay at Universal Orlando to get the free front-of-the-line benefit with a hotel stay there, then use the 10-day Disney ticket to add a day to two at the WDW parks to my Universal Orlando hotel stay.
It's kinda backward to what most people do - adding a day or two at Disney to a Universal Orlando vacation, instead of adding a day or two at Universal to a Disney hotel stay - but it works for us.
For example a 14 day park hopper ticket inc. waterparks\hopper etc will cost approx UK £250 (approx US$375) if purchased in the UK before travel.
I much prefer the size, layout, and comfort of Disneyland and/or Universal Orlando. Two parks, on-site hotels, parking structures rather than huge expansive lots, and overall just a much cozier feel.
If you can possibly swing the cost, I would recommend either the Swan or Dolphin, or the Yacht/Beach Club, as they have boat service to both EPCOT and Hollywood Studios. And with a park-hopper, you can take the boat to EPCOT and then hop not the monorail from there to get over to the Magic Kingdom. You can visit 3 of the 4 parks without needing to ever ride on a bus or in a car.
By the way, all of Hollywood Studios' rides/shows are covered or indoors, so if the forecast calls for rain, it's your best bet.
Even if one is not a fan of the 10-day ticket, there is still no need to pay full price for park tickets. Many ticket resellers have "get a day free" specials or shorter non-expire tickets. Many businesses have discount programs for their employees which have Disney tickets. Just make sure to compare the total price, including tax and shipping, to Disney. I prefer sites which state the full price including tax and standard shipping up front.
The moral, plan ahead and do the math. Get what fits your budget and style of vacationing.