Bobby Fischer, as quoted by Jim Ratliff in a question about increment says:
The result of adjournments is often a skewing of a particular player's chess-playing ability since the success or failure of a player upon resumption of an adjourned game often depends on the amount of time spent analyzing the game during the adjournment as well as the quantity and quality of help that player had in analyzing the game during the adjournment.… Thus, the play of the game upon resumption of the adjournment does not necessarily reflect the ability of a particular player, but rather it may be more a reflection of the ability of his team of analysts, books and computers. There are many people, including the present inventor, who wish to eliminate adjournments for exactly this reason. A chess game should be an accurate reflection of the ability of a particular player and not a reflection of the strength and ability of his team of analysts, books and computers.
It's a good argument against adjournment, but what's the relevance to increments?