Rubber hatch covers deteriorate from exposure to the sun. Depending where you live and how you store your kayak (i.e. indoors or outside, covered or exposed) it is common to need to replace the hatch cover every three to ten years. If you store your kayak outdoors, a boat cover may pay for itself in terms of hatch lids alone (and a kayak cover will reduce fading and weakening of the rest of the kayak too).
Tip: Coat the outside of your rubber hatch covers at least once a year with 303 Protectant to extend their life. 303 blocks the sun's UV rays. Lubricate the hatch cover's seal and the lip of the hatch rim with a thin smear of 303 to make the hatch cover slip on more easily. Lubricating the hatch whenever it feels hard to close helps protect your kayak from cracking around the hatch rim from excess pressure while closing hatch lid. However, be careful not to over do it with the lubricant or your hatch cover may come off too easily.