It depends (4 wks). Right now I am trying to build up the bank in anticipation of extended mat leave #2 (at some point in the next several years).
After that - I will make sure to always have at least a week, just in case.
We are allowed to carry over something like 4 mos worth every year, or something like that.

I build the bank up to its max. I'm just back at the max this year after taking maternity leave 2.5 years ago. So now I will maintain the max, unless I have to use it, and use all the leave I accumulate next year during the year. I'm actually looking forward to "having" to take 4 weeks off next year!

We can only carry over 10 days of Paid Time Off to the following year, so I always use up my time at the end of the calendar year.

I tend to link an Annual Leave day with a long weekend holiday to make a 4 day vacation period.

Depends on the Sick/Personal Leave amounts.

I accrue leave with each paycheck (4 weeks). At the start of each calendar year I sit down and figure out our big vacation, thanksgiving and Christmas plans. We normally budget 1-2 weeks on our big vacation, 1 week for Christmas if we're traveling to my family (every other year. In laws live nearby and we don't take any time off to see them on their year) and then a week for random trips that pop up like weddings, funerals and weekend trips. I have pretty good job security so I only normally have about a week in my leave bank.

My friend who works for a defense contractor is always afraid of being laid off so she always has 3 weeks in her leave bank. If she was laid off it would be paid out to her.

How much time do you save in your annual vacation bank? For example, you have three weeks worth so you use two weeks and save the other week for another time.