We have 5 day PH's for our upcoming trip. I know that is the maximum number of days you can buy, but can you add a day onto that ticket if you want to?
If I recall correctly, DLR stopped selling 6-day and longer tickets back in late 2012. They allowed guests to add days (to get to 6, 7, or 8) for a bit longer, but they no longer allow that anymore. The maximum ticket length is now 5-days, and if guests want anything longer than that, they either have to buy another ticket or upgrade to an annual pass.
It is such a bummer they stopped offering longer than 5 day PH's. We always got at least 6 days, and sometimes up to 8 days. There was a time period in late 2012 and early 2013 when they would let you add a 6th day when you were on the 5th day, but from what I've heard they don't do that anymore at all. A bunch of us wrote to Disney and got some response (I got a phone call back and some fast passes in the mail), but apparently it didn't do any good getting Disney to change their minds.