Yes, it works.

Essentially, every time you cast sanctuary you make a percentage skill check against your haven skill. If it's successful your sanc lasts an extra tick.

This means that having even a 75% haven will give you the bonus 75% of the time, and sanctuary duration does vary slightly to begin with, which can make the bonus hard to see unless you skip practicing haven altogether.

In essence the premise is the same, as you're still going to get either 5 or 6 hours sanc, but with mastered haven, numericly the occurence of 6s will have increased to what it would have been if you hadn't?

Is that about right?

Nope.

Let's say the standard sanc duration for your level is 5 hours.

Sanc duration varies a little bit so it'll be 4 sometimes, 5 most of the time, 6 sometimes.

If you had let's say 75% haven that would be further complicated to be more like: 4 rarely, 5 sometimes, 6 most of the time, 7 sometimes.

Edit to add: And if you had 100% haven at that same level it would be 5 sometimes, 6 most of the time, 7 sometimes. You would never get the 4.

Because you're *usually* getting the benefit of haven if you've practiced it even to learned, you probably are assuming the base duration of sanc is higher than it actually is because you're used to getting its bonus most of the time. 100% haven just means you'll *always* get the bonus.

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