How does Critical Ascension work?

The Assassin/Zero's Critical Ascensi0n skill stacks bonuses from Sniper Critical Hits. The stacks slowly decay, but over how much time? How can I check how many stacks I have? How can I tell if it's active at all? Does scoring a new Crit Hit preserve the whole stack for longer, or just the latest stacks? How can I prolong the stacks' effects?

User Zikel, in the /r/Borderlands subreddit has tested Critical Ascension and came up with the ff. results:

You start losing stacks after 6 seconds.

You lose 1 stack per second.

Switching weapon, opening a menu (map, inventory, quest log, etc), using a vending machine, talking to a quest giver and dying instantly removes all stacks.

You can melee, throw grenades and sprint without losing all stacks!

^{Source: Reddit /r/Borderlands post by user Zikel, "Many skill descriptions are misleading, don't tell the full story or straight up lie to you. I took it upon my self to test EVERYTHING and clear up the confusion. Here are the results."}

They start to decay in 6 seconds. After about 12 seconds, they decay rapidly. You lose about 70 stacks in about 10 seconds or less. This limits the utility of the skill greatly.