If the product license is Checked for Future Updates and 6 months support, how long do the Future updates last?
Future Update version of the Item you will get the entire life of the Item. Support only for 6 month initail with all Items(except Auhtor not mentioned that they not provide support) but after expired you can extend any time.
Agree with @mgscoder
Even if you get the item with default support (the 6 months) or with the extended support, you can re-download the item at any time.