2 years ago I pulled one of our hatches 20 years after being sealed with butyl tape. It was still sticky and gooey and had no leaks. Aside from the good seal the clean-up is easy with mineral spirits. I put in some monofilament fishing line spacers either side of the screws so I could pull it down snug and keep about 1 mm (that's 1/25th of an inch) of sealant in. The fishing line was pieces about 12 mm (1/2 inch) long and embedded in the butyl. It did ooze a bit for about a month then stopped. No leaks on that one or any of the others that have now been in place for 22 years.