I guess it all depends on you and your traveling style.
If you are gonna be in tourist hot-spots at the height of the tourist season it will he harder to find a cheaper place. If you have a strict budget to stick to it may be better for you to book something in advance. On the other hand if you're a happy-go-lucky type of a traveler, then you can always arrive to the new destination and go to the tourist info office and hope they can hook you up with accommodations.
"Growing old is manditory, growing up is optional"