Time for new ones. My Shimano Ultegra 6700 hoods lasted about 36,000 miles, 6 1/3 years. I’m a heavy user of the hoods since I do a lot of climbing and descending.
My only experience with gum hoods was Campagnolo Nuovo Record from the old days. They cracked with age. Shimano doesn’t crack, but when they’re loose they’re just as worthless as cracked Campagnolo.
It’s an easy fix that will set you back about $12. I just cut off the old ones. You’ll need some muscle to get the new ones on. Use some hand sanitizer for lubrication. Liquid soap, Dawn or the like, also works, but the sanitizer evaporates better.
The primary concern is with the rubber lip in the front. The little bumps inside fit into holes in the handle. There are MANY different styles. Some may overlap for use, but I didn’t want to take a chance so I found the exact match.