Just sudsy soap & water with a "once-in-a-while" brushing is a kiss of bore death if you are using plastic and copper. Also traces of leading could build-up unsuspectedly.... sending comatose barrels to places like auctionarms.com -- where I buy them from soap & water folks - give them some life-restoring solvent medicine & re-sell them.

Don't be skimpy with your investment! Use a "proper" solvent & use a hard shell, air-tight, poly-foam gun case for best protection from open air & temperature changes.... not a non-siliconed soft case.