Sitting it in the sun has nothing to do with drying the material. Its about the sun warming the rubber so it will lay and settle into position. Also, though the butyl doesn't dry, it does become a lot less liquid like and sort of grabs onto the glass and the metal better after its a few months old.

My wife's PT got a cracked windshield (it was bonded in, no gasket), we had it replaced, but the installer cracked the new glass upon the installation (he was working alone), it had to set up for 3 weeks before they (2 guys the second time) could replace it because the butyl would have been too messed up to remove it. Even after 3 weeks, it was still pretty messy. The new windshield has been in the PT for 14 years, no leaks yet.

The glass has been in my truck for 4 or 5 months now and about the last month, its sat outside all the time, he wasn't going to water test it right after he installed it, he wanted it out in the sun for a while.