How to efficiently plan holidays in academia? It is holiday season, so I thought of re-considering my ways of holiday planning. 

As a student, holidays in academia are somewhat shaped by the semester breaks and the lecture-free period. Working in academia things are slightly different. One still has to be available during the lecture times, also account for the deadlines and additional tasks. 

Each time I want to plan some holiday, I remember my yearly tasks, and then I see that I don't have time to relax. Work seems to never end, I have to stay there in the office and prepare the exercises, work on the project, write paper etc. etc. 

There is clearly something wrong with this, and I want to change it. But, I don't know how to distribute my holidays throughout the year, because I've been used to working all time. How often should I take holidays?

I know this question is somewhere between workplace and academia. And I know it also may provoke many opinion-based answers. But, I would like to know the different approaches from the more experienced people.
I tend to combine my holidays with academic travel. In part, because it reduces the cost of going to conferences: I don't have to fly half way across the country just for two days. In part, it also reduces the monetary cost of holiday travel.

For example, adding 2 days for sightseeing/relaxing after a conference doesn't impact flight reimbursement. You pay for the hotel/airbnb, but that's it. That is especially appealing if you are going to a conference in Europe [US] and you're based in the US [Europe], such that the flight is a substantial part of the cost.

I've also gotten flights to other cities reimbursed. As long as the flight X -> Y -> Z is not more expensive than X -> Y -> X, neither my university nor others that have paid for my travel have had any objections. It almost always costs them less (and never more), so it's a win-win situation. In that case, I still end up paying Z -> X, but that's half the fare I'd otherwise pay. If the flight to Z costs more than to X, I let them know and claim less than the actual cost for reimbursement.

Another advantage of this is that it spreads out vacation days throughout the year. I never feel guilty taking off a day here and there and I'm substantially more productive afterward. Doing nothing for two weeks doesn't particularly appeal to me and would likely just stress me out once I got back.