What does "整块的时间" mean?
Can I share my thoughts after the OP has chosen the best answer?

I disagree with everyone here: 整块的时间 is correct, and I hear people say it all the time.

If you Google the phrase "整块时间" (commonly used without 的), you see a lot of test prep  websites suggesting that students use an entire block/period studying for one subject as opposed to spending ten minutes on history when you wait for the bus and another ten before they go to bed (i.e. 用整块时间学习). The opposite is 零碎时间, which means "fragments of time" (five minutes today, five minutes tomorrow).

For example,


  你今天得把文章写完！You have to finish your article today!
  
  根本不可能！我五分钟之后要开会，会结束之后十分钟又要参加开幕式！It's impossible! I have a meeting in five minutes and only a ten-minute break before the opening ceremony starts! (Here, if you combine the speaker's five- and ten-minute breaks, he could probably finish the article. But unfortunately he does not have 整块的时间 - only 零碎的时间.)


Similarly, 爬山 takes up 整块的时间 (can't be done during those five-minute breaks) because it's exhausting, not to mention the traffic and the mountain's location. The book is trying to illustrate that "一年中能悠闲地爬那么一两回，已经算是十分的心满意足了", as 爬山 usually takes a day or two.

P.S. Is there an English equivalent of 整块的时间? I can't think of any off the top of my head.

EDIT: Aelephant suggests "a relatively long period of uninterrupted time" - perfect!