The guarantee is the time you get paid to fly weather you fly them or not.
If you fly ten hours in a month you still get paid for the full guarantee. Those are flight hours and not time at work.
A pilot may work 100 hours to get 40 hours of flight time.
At my airline we have a 60 hour minimum pay guarantee for the month. But we also have 10 G days (guaranteed days off per month. These G days are all in a row. So the airline has 20 days per month to try and fly us the 60 hour guarantee. During that 20 day peiod we also have to meet the minimum crew rest times also.
That is why it is better to fly long trips than short ones. It is better to fly 6 10 hour trips then 10 6 hour trips. Thats 4 less trips to the airport, and 4 less preflights, and 4 less everything.
If you aren't going to break your monthly guarantee it is to the pilots advantage to work as little a spossible. If you fly 4 hours or 60 hours you still get the same pay.
If you do break your monthly guarantee then you get paid your hourly rate, which in my case is 58 per hour.
On my time off I sleep, sleep ,sleep. And on my G days I usually take advantage of my travel benefits and jumpseat all over the world. Ten days off in a row is alot. It sucks during the day when everyone has to work and there's no one to hang with.
Some companies have a 2 week on and 2 week off schedual. Imagine having 2 weeks off a month every month. I'd go even crazier.