V1's are GT's that have not been brought from the classic xbox over to the xbox 360. V1's reset after 7 years of not being played on so for example if someone stopped playing on a gt in 2002 the gamertag would reset in 2009 which makes it available for anyone to take. Every tag differs in the time because some tags have been played on others haven't.
It's gamertags on the original Xbox not 360 and no one knows in defiantly when they get reset just can guess run 24/7 turbos on them but if they have a spaced version on Xbox 360 its pointless
V1's are accounts which were made on the original 360's.
You know a account is V1 when either of these come up.
No-one ever knows the timing for a V1 reset, it's all automated, and Xbox employees won't even answer the question in live support chat, also if you have a space gamertag, like "Devour" he has "B oy" when the gamertag "Boy" resets, "Devour" will be the only person which can change the tag, because whenever someone else tries it will say "Boy" is already taken, when "Devour" tries, then it'll let him change it, so that's a good thing about a space gamertag.
Hope you understand, loads of detail here, message me for more.