Quick question for everyone...

I was told that unused WDW passes could be used at Disneyland for admission -- specifically, that if I had a 5 day WDW ticket and used 3 days, I could use the remaining two at Disneyland. Is this true? Are there any catches I should know about? I'm asking as the new WDW "Magic Your Way" tickets have a lovely "no expiration date" option, which means I could buy a 10 day ticket at about $23 a day and use the 10 days over three years...