Most experts agree that caulking and weather stripping any gaps will pay for itself within one year in energy savings. Caulking and weather stripping will also alleviate drafts and help your home feel warmer when it's cold outside.
You can extend the the time it takes hot-melt glue to set by slightly pre-warming both the surfaces to be joined with a heat gun. A heat gun also works great for stripping paint and other odd jobs. For example, you can use it to remove bumper stickers, defrost freezers, char-stain wood, dry wood for painting, burn weeds from cracks in sidewalks and patios, light charcoal, loosen rusted bolt nuts and bend certain plastic piping.