I don't have many secrets but this is one of the best I have.

Use this stuff and your plastics will not dry out. It gets better with age. A little goes a long way.
http://www.bassbuckandduck.com/Craw-Cane-Attractant.html
I am a big believer in this stuff. Not easy to find.

Worm oil, pick your scent
http://www.pouryourownworms.com/Scented-Worm-Oil-and-Marinades-2-oz-Scented-Worm-Oil-2oz.htm
also keep your plastics stored in a cool dark place, sunlight along with wide temperature swings will deteriorate them, the ones with salt will degrade fastest.

FYI, cabelas has their utility binder replacement bags (aka soft plastics) on sale for $1.88 per 8 right now.

check their rock bottom deals in the bargain bin.

thanks for the tip curtbass ---went to krogers came in a little 1 oz bottle about 2 bucks
an ounce didnt seem like much but it goes a long way
it also seems to have alcohol in it but it did do a good job
came in a little bottle -- took the cap off and punched a little hole in the paper seal -dripped perfectly !

Not alcohol. Anise is a strong scent. It also what they flavor licorice with.

+1 I have been using this oil for many years.

There are also a bunch of scents on the market that are made for soft plastics that can be used also. Academy has a pretty good selection of them.

its called Mineral Oil, it can be found at your local drug store for cheap, I have been restoring plastics for over 30+ years with it, it is odorless and goes a long way, less that a cap full will oil a good size bag... majority of large plastics manufactures use it they just add scents to it like anise oil... try it you will see...

Mineral oil works great.